Answer:
You would do this problem like a normal varible problem. x=10
Explanation:
Since 9x is a right angle the inside would also be 9x
9x+4x+10+40=180
180 because that is how much a triangle equals
combine like terms
13x+50=180
subtract 50 from both sides
13x=130
divide by 13
x=10
Hope this helps!