Can someone please help explain this, my notes aren't helping me much.

Question

Given the following system of linear equations:

{x-4y=20
-3x+4y=-12

The solution to the system is:

The system is:

The equation is:

Please help

Answer 1

x-4y = 20
-3x+4y = -12

add them together and you get

-2x = 8
x = -4

Now use that to get y.

Answer 2

do you plug it into the first equation or the second?

Answer 3

i got it thanks