Answer:
145°
Explanation:
The exterior angle 3 is equal to the sum of angle 1 and 2.
Using substitution we can say that:
5x + 4x + 10 = 10x -5
9x + 10 = 10x -5
10x-9x=10+5
x= 15
We have just found that the value of x is equal to 15.
By substituting this back to the angle 3 expression, 10x-5, we get
10(15) - 5
150 - 5
145°