Answer:
99°
Step-by-step explanation:
∠7 and ∠8 are a linear pair, so are supplementary. Numbers are assumed to be degrees.
∠7 + ∠8 = 180
2x+15 + 3x = 180 . . . . . substitute given values
5x = 165 . . . . . . . . . . . . subtract 15, collect terms
x = 33 . . . . . . . . . . . . . . . divide by the coefficient of x
∠8 = 3x = 3·33 = 99 . . . . . degrees
