Question

Have a question:
-x + 3y = 12 and y = 5
Would x = 3 or -3?

Answer 1

y = 5

so

-x + 3y = 12

turns into

-x + 3*5 = 12

after you plug in y = 5

Answer 2

-x + 3*5 = 12

-x + 15 = 12

-x = 12 - 15

-x = -3

We want x, not -x, so change the sign of both sides to get

x = 3

Answer 3

Thank you Jim, I thought it was 3 but I wasn't completely sure, I forgot to change -x to a positive. Thanks again!

Answer 4

you're welcome, glad to be of help