y=x+16
y=-x+4
All you have to do is substitute.
Put the second equation into the first equation.
-x + 4 = x + 16
4 = 2x + 16
-12 = 2x
-6 = x
Now substitute the x into one of the equations to get y.
y = (-6) + 16
y = 10
The solution to these equations is (-6, 10).