Answer:
x = 11, ∠ B = 71°
Step-by-step explanation:
In a parallelogram, consecutive angles are supplementary, that is
∠ A + ∠ B = 180°, thus
8x + 21 + 5x + 16 = 180
13x + 37 = 180 ( subtract 37 from both sides )
13x = 143 ( divide both sides by 13 )
x = 11
Thus
∠ B = 5x + 16 = 5(11) + 16 = 55 + 16 = 71°
