Answer:
x=16
y=40
Explanation:
x + y = 56
y = 56 - x (isolate a variable)
y = -x + 56 (this is optional)
2x = .5y + 12
2x = .5(-x + 56) + 12 (substitute for y)
2x = -.5x + 28 + 12
2x = -.5x + 40
2.5x = 40
x = 16
16 + y = 56 (plug what you got for x back into the original eq)
y = 40