You are expected to know that adjacent internal angles of a parallelogram are supplementary: they add up to 180°.
... (5y)° + (9y + 68)° = 180°
... 14y + 68 = 180 . . . . . . . . . . collect terms
... y = (180 - 68)/14 = 8
Then ...
... m∠B = (9·8 + 68)° . . . . . . . substitute 8 for y in the expression for m∠B.
... m∠B = 140°