Answer:
96°
Explanation:
In a cyclic quadrilateral (one inscribed in a circle), opposite angles are supplementary. That means the angles marked (6m+13)° and (4m+7)° have a total value of 180°:
(6m+13) +(4m+7) = 180
10m +20 = 180 . . . . . . . . collect terms
m +2 = 18 . . . . . . . . . . . . .divide by 10
m = 16 . . . . . . . . . . . . . . . subtract 2
∠M = 6m° = 6·16° . . . . . . . use the value of m in the expression for ∠M
∠M = 96°