Answer:
∠B = 17°
Step-by-step explanation:
Vertical angles are congruent, thus
5x + 7 = x + 15 ( subtract x from both sides )
4x + 7 = 15 ( subtract 7 from both sides )
4x = 8 ( divide both sides by 4 )
x = 2
Hence
∠B = 5x + 7 = (5 × 2) + 7 = 10 + 2 = 17°
