Question

How do you solve by substitution `x - y = 6` and `x + y = -2`?

Answer 1

`x-y=6`
Thus `color(blue)(x=6+y` ( we add `y` on both side )

Now that we have `color(blue)x`, we can replace it in the second equation :

`color(blue)x+y=-2`
`color(blue)(6+y)+y=-2`
`6+2y=-2`
`2y=-2-6` ( we substract `6` on each side )
`2y=-8`
`color(red)(y=-4` ( we divide by `2` on each side )

Now that we have `color(red)y`, we can find `color(blue)x` :

`color(blue)x=6+color(red)y`
`color(blue)x=6 color(red)(-4)`
`color(blue)(x=2)`