PLEASE HELP
This is my third post of this! I really need help

x=25

solution:

we know that
The triangle external angle theorem states that: An exterior angle of a triangle is equal to the sum of the opposite interior angles

In this problem:
m∠9=m∠7+m∠8

substitute the given values:
(6x-20)°=30°+4x°

now solve for x:
6x-4x=30+20
2x=50
x=25 which is the final )