Answer:
15) 8
16) -2
Explanation:
For each problem, use 4 where there is an x and -3 where there is a y!
15) 11+y=? If y=-3 it is 11+(-3) and that is 8!
16) x+(-6)=? If x=4 it is 4+(-6) and that is -2!
The other ones seem to be missing something so I don't understand those, but if you need more help reply to this and I'll help!