Step-by-step explanation:
The sum of interior angles of a triangle is 180 degree
x + (180 - 3x ) + ( 180 - 2x - 72 ) = 180
x + 3x - 2x + 360 - 72 = 180
2x + 288 = 180
2x = 108
x = 54
L = 180 - 3x = 180 - 54*3 = 18
x + L + M = 180
54+18+M = 180
M = 108
