Answer:
x = 25
Step-by-step explanation:
The Exterior Angle Theorem states that the exterior angle of a triangle is equal to the sum of the two opposite interior angles.
This means that
3x - 10 = 25 + (x+15)
3x - 10 = x + 40
Subtract x from both sides of the equation.
2x - 10 = 40
Add 10 to both sides.
2x = 50
Divide both sides by 2.
x = 25
