Question

Solve for y

0.4x-0.3y+12=0

says the answer is y=4/3x+40

I did 0.4x-0.3y=-12
-0.3y=-12-0.4x
y=-12-0.4x/-0.3?

Answer 1

one idea might be to multiply everything by 10 and start with
4x - 3 y + 120 = 0

Answer 2

you solving for y right?

Answer 3

yes, why would you multiply by 10?

Answer 4

to get rid of the annoying decimals
you don't have to do that, you will get the same answer working with the decimals
lets do it both ways

Answer 5

after multiplying by 10 and getting
4x - 3 y + 120 = 0
add 3y to both sides and get
4x + 120 = 3y
divide both sides by 3 and get
4/3 x + 40 = y

Answer 6

ohhh gotcha!

Answer 7

i understand it after multiplying by 10. the decimals threw me off lol

Answer 8

working with the decimals, add .3y to both sides and get
.4x + 12 = .3y
divide both sides by .3 and get
.4/.3 x +12/.3 = y
but .4/.3 = 4/3 and 12/.3 = 120/3 = 40 so you still get
4/3 x + 40 = y

Answer 9

yeah decimals are a pain, that is why it is nice when you can eliminate them
but if you multiply by 10 make sure to multiply everything by 10
in this case you have to remember to multiply 12 by 10 to get 120

Answer 10

can you help me with 4/5x-2/3x+8=0 I'm stuck with this one too.

Answer 11

are the x's outside of the fraction?

Answer 12

(4/5)x-(2/3)y+8=0

Answer 13

oh that is a y!

Answer 14

multiply everything by the least common multiple of 5 and 3, which is 15

Answer 15

yeah sorry typo :)

Answer 16

by multiply, i really means cancel what you can
so if you multiply all by 15 you get
12z - 10 y + 120 = 0

Answer 17

typo there, the z should be an x

Answer 18

then subtract 120 to both sides?

Answer 19

you are solving for y right?

Answer 20

i would add 10 y to both sides and get
12x + 120 = 10y

Answer 21

Yes, I got it! :) y=(6/5)x+12

Answer 22

yes, that is the right one
hope it is clear why and how i multiplied all by 15

Answer 23

what about (y-2)/(3)=(x+3)/(4) ? Do I multiply everything by 12?

Answer 24

you can do that, yes

Answer 25

so, 12y-24-12x+36?

Answer 26

don't forget parentheses
get 4( y - 2 ) = 3( x + 3)

Answer 27

12y-24=12x+36 * typo

Answer 28

errr um what?^

Answer 29

when you multiply by 12 you are cancelling

Answer 30

hold on i will write it out

Answer 31

I figured it out! :)

Answer 32

be a lot easier of the stupid equation thing was working
here goes
(y-2)/(3)=(x+3)/(4)
multiply by 12 get
12(x - 2)/3 = 12( x + 3)/4
now cancel
3 goes in to 12 4 times, and 4 goes in to 12 3 times
oh good

Answer 33

y=3/4x+17/4

Answer 34

yay