Question

What is the value of the y variable in the solution to the following system of equations?
2x + y = 5
x + 3y = 0

A –1
B 1
C 3
D –3

Answer 1

You need to use elimination to get rid of the x variable and leave only the y. To do that you need to get the coefficient of x as the same value. So multiply the second equation by 2 to get 2x + 6y = 0. Then take that equation away from the first one.
The 2x and 2x cancel and y - 6y = -5y. That leaves -5y=5 so y = -1.

Answer 2

\[2x + y = 5\]\[2x + 6y = 0\]

Answer 3

you could also use substitution

2x + y = 5
is the same as
y = 5 - 2x

so then
x + 3y = 0
becomes
x + 3(5-2x) = 0
or
x + 15 - 6x = 0
5x = 15
x=3

Answer 4

Yeah but make the formula equal to x so you can substitute that in and find y.

Answer 5

thank you all for your help but i have to give the medal to @alrightatmaths because he had the right answer but thanks again!