Here's the solution,
=》 C + 112° = 180°
( they form linear pair )
=》 C = 180° - 112°
=》C = 68°
And we know, measure of exterior angle if a triangle is equal to the sum of measures of the opposite interior angles,
So,
=》B = C + 51°
=》B = 68° + 51°
=》B = 119°
