the answer is 42+12=17
and this is how to double check
42+12=17
16+1=17
17=17
17?
2 & 17
28
9 and 8 because if you add them you get 17 and if you subtract them you get 1
17
The two numbers are -2 and -15
No two of those numbers add to 17.
17?
2 & 17
28
8 + 9 = 17
2 and 17
17 and 13
17 and 7
9 and 8 because if you add them you get 17 and if you subtract them you get 1
17
-17