Answer: 23
Explanation:
Vertical angles are congruent (equal) so you first make the equations for angle A and B equal to each other and solve for x.
x + 15 = 5x - 17
32 = 4x
x = 8
Plug the x value (8) back into either equation to find the measure of angle B.
x + 15
8 + 15 = 23