Question

Need help with Geometry math

problem #9

Answer 1

Let ABC be a triangle such that CA is produced to meet at E.

We know, an exterior angle of a Triangle is equal to non- adjacent interior angle, so

8x - 10 = x + 15 + 2x + 20

or, 8x - 3x = 35 + 10

or, 5x = 45

or, x = 9