Answer:
80°
Explanation:
The sum of the two angles (red and blue) is 145°, so you have ...
(4x +5)° +(6x -10)° = 145°
10x = 150 . . . . . . . . divide by °, add 5, simplify
x = 15 . . . . . . . . . . . divide by 10
Then the measure of the angle of interest is ...
m∠XMN = (6x -10)° = (6·15 -10)° = 80°