Answer:
One solution, x = 8/9
Explanation:
One way to solve this is to take one equation and substitute into the other and then solve. So, take y=5(x-4) and put that into the other equation.
4x + 12 = -y
4x + 12 = -(5(x-4)) <--- substitution here
4x + 12 = -5(x-4)
4x + 12 = -5x + 20 <-- simplifying
4x + 5x = 20 - 12
9x = 8
x = 8/9