In order to solve for the point of intersection between these two lines, we need to use the addition method. An example of the addition method would be something like:
y = -1x + 2
y = 1x + 3
_________
2y = 0x + 5
Hopefully that makes sense. We can essentially use that on these two equations in the given:
y = -2x - 20
y = 1x + 4
But wait! If we add these two functions now, there'll still be two variables! We have to get rid of one. To do this, multiply the second equation by 2:
y = -2x - 20
2y = 2x + 8
_________
3y = 28
y = 28/3
Input 28/3 into one of the equations to solve for x:
28/3 = x + 4
28/3 = x + 12/3
x = 16/3
(16/3, 28/3)
-T.B.
