The numbers

Question

38, x, -8, and y
form an arithmetic sequence. Compute
x+y

Answer 1

I can find x-y but not x+y

Answer 2

x-38 = -8-x
so
2 x = 30
x = 15

-8-x = y -(-8) = y+8
-8 - 15 = y + 8
-23 = y + 8
y = -31

x+y = 15-31 = -16