Question

How do I solve for x

Answer 1

5x - 15 = 3x + 1

5x - 3x = 1 + 15

2x = 16

x = 8

5 · 8 - 15 = 25° and 3 · 8 +1 = 25° OK !

⇒ 20x - 5 = 180 - 25 = 155°

Verify:

20 · 8 - 5 = = 160 - 5 = 155° correct

Answer 2

In other cases look for opposing angles that are equal, etc.