Question

I can't solve x=-4y
3x+2y=20

Answer 1

The answer is -2 because

x=-4y
plug in -4y where x is in the equation

3(-4y)+2y=20

then multiply -4 and 3 which equals -12

so now you have -12y+2y=20

combine like terms

-10y=20

now you solve
20/-10=-2

Answer 2

x= -4y

3x+2y=20

Now you see that you are given the value of 1 variable (x) so you can sub it into the second equation, and then solve as usual.

3(-4y)+2y=20
-12y+2y=20
-10y=20
-10y/-10=20/-10
y=-2