Angles XQL and MQR are congruent because they are vertical angles. So
209 - 13 b = 146 - 4 b
Solve for b :
209 - 146 = 13 b - 4 b
63 = 9 b
b = 63/9 = 7
Then the measure of angle XQL is
(209 - 13*7)º = 118º
