Which equation can be used to find the unknow ange measures?

The diagram is a triganle. A= x+30, B= 3x, and C = x-15

A 5x+15=90
B 5x+45-180
C 3x^3+15=180
D 5x+15=180
E 3x+30=180

1 answer

Assuming A, B, and C are the angles, then

x+30 + 3x + x-15 = 180
5x + 15 = 180