Question

What is the value of the x variable in the solution to the following system of equations?
7x - 2y = 21
4x + y = 57

Answer 1

ummm is this algebra 2?

Answer 2

algebra 1, 2nd year taking it again

Answer 3

once i find the y , i put it in the the first equation right?

Answer 4

I think so... i asked somebody if they could come and help since I need to understand this better as well since i sort of forgot haha :)

Answer 5

sorry hold on lemme see if that person will come... ;/

Answer 6

okay thank you (:

Answer 7

Hi @jim_thompson5910 thanks for coming :) I also do not understand this 100% haha :) u got my message then i take it? :)

Answer 8

double everything in the second equation to get

8x + 2y = 114

Answer 9

sorry (email)

Answer 10

and hi @apoorvk thanks for coming also!!! i appreciate it :)

Answer 11

ohkay, @iheartfood - go on and post what you would have done in this problem, and don't worry if it's right or wrong.. :)

Answer 12

Now add the two equations

7x - 2y = 21
8x + 2y = 114
--------------
15x + 0y = 135


Now solve 15x = 135 for x

Answer 13

well i know you're supposed to solve for one, but i did not know you could do that (what @jim_thompson5910 wrote.... so that is another way you can do it??

Answer 14

is that how you do it?? simplify it into one larger equation??

Answer 15

that's one way to do it, there is more than one way

Answer 16

okay, what's another way to do it?? i think i remember that you can solve one equation and then plug it in but i couldn't do it for this one... ;/

Answer 17

you isolate one variable in terms of the other

then you substitute


4x + y = 57

y = 57 - 4x

------------------

7x - 2y = 21

7x - 2(57-4x) = 21

Now solve for x

Answer 18

x = 9 for my problem right? (:

Answer 19

oh okay cool :) soooo x=45??

Answer 20

you are correct, the answer to the first piece is x = 9

Answer 21

oops my bad nvm lol

Answer 22

hmm how did you get x = 45?

Answer 23

now that you know that x = 9, use this to find y

Answer 24

sorry by bad... lol it's 9 sorry!!

Answer 25

sooo you plug it in right??

Answer 26

so y=21 ???? and x=9 ???

Answer 27

yes, pick any equation dealing with y and plug in x = 9

7x - 2y = 21

7(9) - 2y = 21

Solve for y

Answer 28

and yes, y = 21

Answer 29

oh i used the second equation.. haha but it works both ways :) u get the same answer for both right?

Answer 30

oh the question was just "What is the value of the x variable in the solution to the following system of equations?"

so they just want x

Usually, they'll want both x and y

Answer 31

yes either equation works

Answer 32

oh okay cool! thanks!! i totally understand it now... :) what a refresher!! And @sommersquid did that help??? And thanks again for coming @jim_thompson5910 :)

Answer 33

yesss, it really did (: i just needed help with the second step but i got it now (: thank you so much everyone

Answer 34

yw