Question

Given: x + y = 6. If x {-15, -6, -1},

Answer 1

x+y=6
x=-15+-6+-1
x=-22
Then
if x+y=6
-22+y=6
y=22+6
y=28

Check
-22+28=6

Answer 2

First case
x+y=6
-15+y=6
y=6+15
y=21

Second case
x+y=6
-6+y=6
y=6+6
y=12

Third case
x+y=6
-1+y=6
y=6+1
y=7