Answer:
Your answer will be 17˚
Explanation:
1. You find the measures of the known angles (Which A = 51˚ and C = 112˚).
2. You find the unknown angle.
3. You add up both the measures of the known angles (which are A and C).
4. Take the sum of the two known angle measures and subtract that from 180.
5. You end up with the now known measure of angle B, which is 17˚.
That was a lot of explaining, but hope that helped you out.