Question

Please help me with this mathematical equation? It's not making sense to me in the least. Thank you.

Solve the following system using the substitution method.

10x - 3y = -7
5x - y = -2

Answer options:

-1/5, -3
1/5,-3
-1/5, 3
1/5, 3

Answer 1

Take one of the two given equations, substitute the value of y in terms of x then substitute it the other equation.

Answer 2

how so?

Answer 3

10x - 3y = -7
5x - y = -2

isolate y from the second :

y= 5x + 2
now plug it into the first :
10 -3(5x+2) = -7
now you will get a x value ..
can you tell me what is it ?

Answer 4

OH what am i saying? I understand this

Answer 5

10 (-1,5) - 3 (-3) = 7

Answer 6

Answer A is crossed off the list

Answer 7

Instead of trying to check the answers (which is a valid option in this case)
you might try and really solve the system ..

Answer 8

My error

Answer 9

Let's continue

Answer 10

read my first response

Answer 11

i'm solving for x?

Answer 12

yes then after we will have x value we can find y value..

Answer 13

God I don't know this. I seriously don't. I'm alien to this whole stupid concept.

Answer 14

again :

we had two equations :
10x - 3y = -7
5x - y = -2

now, in order to get the solution
we have to solve first for one variable and then using the solution for this one variable
we will get the other.

we can do this by two methods : one- substitution and the other is - elimination

in here we have been asked for the substitution :
so we find an expression for one of the variables in term of the other from one of the equation

in this case i chose to use the second equation and isolate y from it
and get :
y = 5x + 2

now since i got it from the second equation ill substitute it into the first
ill replace y by what i got from the first equation
and then ill have an equation with only one variable - x ! which is easy to solve.

Answer 15

after substitution in the first we have :
10x - 3 * (5x + 2) = -7
tell me please if you understand what i wrote so far

Answer 16

Why're you multiplying 10x - 3 * (5x + 2) = -7?

Answer 17

from the second equation i got
y = 5x + 2

the original first equation is :
10x - 3y = -7

now i want to substitute the expression of y that i got from the second equation into the first
so i replace y by 5x + 2 :
10x - 3 *(5x + 2) = -7

Answer 18

So by substiting the expression, you multiply? all the time?

Answer 19

How is that "replacing"?

Answer 20

the same as if i have x = 3
i know that
4x = 12
since

4 * 3 = 12

Answer 21

Oh, well that makes sense

Answer 22

Not multiply so much as replacing every instance of 'y' with whatever you came up with (when you isolated y in one of the equations)

Answer 23

Thank you for clearing that for me :)

Answer 24

so in this case it is the same
i know that y = 5x + 2
then i replace y in the first equation by 5x + 2

Answer 25

10x - 3 * (5x + 2) = -7

So in order to solve this, we need to find x

Answer 26

Would I use the second equation to substitute?

Answer 27

can you solve it now ?:
10x - 3 * (5x + 2) = -7

Answer 28

this is one equation with one unknown .. just simplify it and isolate x

Answer 29

It equals -18 without the x's

Answer 30

10x - 3 *(5x + 2) = -7
10x - [ 3*5x + 3*2 ] = -7
10x - [15x + 6] = -7
10x - 15x - 6 = -7
-5x = -1
x = 1/5

Answer 31

solving such equation should be familiar to you

Answer 32

The answer I got is B with my notes

Answer 33

wait .. now we have x = 1/5
how do you find y ? now you substitute x = 1/5 into one of the original equations..
show me please how you do it

Answer 34

please read all my notes here and tell me if you understand

Answer 35

10x - 3y = -75x - y = -2

10(1/5) - 3y

Answer 36

dont forget the right side of the equation :
10(1/5) - 3y = -7

Answer 37

so now isolate y .. what do you get ?

Answer 38

10(1/5) - 3y = -7

To isolate y I would have to substitute? with the other equation?

Answer 39

no .. this is an equation with only one unknown ..
you just simplify and solve for y
just the same as i did here :
10x - 3 *(5x + 2) = -7
10x - [ 3*5x + 3*2 ] = -7
10x - [15x + 6] = -7
10x - 15x - 6 = -7
-5x = -1
x = 1/5

Answer 40

you substitute in order to get an equation with only one variable .. but you have it already so now you just isolate y..

Answer 41

Ok

Answer 42

so.. solve this:
10(1/5) - 3y = -7

Answer 43

I understand that I've found x

Answer 44

To isolate why I subtract something from both sides?

Answer 45

i dont understand you

if you know x = 3 for example
tell me what is y
if y = 4x ?

Answer 46

4(3)

12

Answer 47

and if you knew x = 3 and you wanted to find y if
y - 2x = 3
?

Answer 48

y - 2(3)= 3

y - 12= 3

12+ 3 = 15

15 - 12 = 3

Answer 49

where is y :|

Answer 50

y-2(3)=3 the first line is good
now
y-6=3 (dont know why you wrote 12) .. now find y

Answer 51

Huh? Now I'm confused

Answer 52

you had this :
y-2(3)=3
now
y - 2*3 = 3
y - 6 = 3 (its not y -12 =3 .. i dont understand why you written -12 instead of -6)

now find y using this equation

Answer 53

How the heck do I solve something I don't know the number to?

Answer 54

y-6=3
you add 6 to both sides of the equations ..
y - 6 + 6 = 3 +6
y = 9 !

Answer 55

Oh:)

Answer 56

My final answer's D

Answer 57

yes because

10(1/5) - 3y = -7
2 - 3y = -7
-3y = -9
y = 3

so 1/5 , 3

Answer 58

THANK GOD

Answer 59

please try and solve this system ..
i want you to understand and do it :

y + x = 3
2y + 3x =7

Answer 60

show me what you do .. i really want you to understand

Answer 61

I do, it's all written, step by step :) that's why I said what I did, since I finished it off

Answer 62

will you try doing this ?
y + x = 3
2y + 3x =7
please

Answer 63

i mean as you wish .. i just want you to be able to solve this by yourself

Answer 64

One moment

Answer 65

i want to understand as well, and from what i see on my paper, I do

Answer 66

ok.. as you wish :)