Answer:
x = -5
Step-by-step explanation:
x + y = 5 can be also written as 3x + 3y = 15 by times 3 on both side, let it be equation (1), then let 2x + 3y = 20 be equation (2), then use equation (2) - (1), can get (2x - 3x) + (3y - 3y) = 20 - 15 ---> -x = 5, then x = -5.
