Answer:
∠B = 130°
Step-by-step explanation:
The opposite angles of a parallelogram are congruent, thus
∠D = ∠B, that is
10x - 20 = 9x - 5 ( subtract 9x from both sides )
x - 20 = - 5 ( add 20 to both sides )
x = 15
Hence
∠B = 9x - 5 = (9 × 15) - 5 = 135 - 5 = 130°
