Question

How cam I solve this math problem

Answer 1

Hello!

180° - (42° × 2) = 96° (Base ∠ of isos. ∆)

C = 180° - 96° - (x + 12°) (Adj. ∠ on a straight line)
C = 180° - 96° - x - 12°
C = 72° - x

(2x + 9°) + (3x - 1°) + (72° - x) = 180° (Sum of ∠s in at ∆)
2x + 9° + 3x - 1° + 72° - x = 180°
4x + 80° = 180°
4x = 180° - 80°
4x = 100°
x = 25°