answer: 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 answer:)
