Answer:
Ext angle = 93°
Explanation:
The angle marked 4x + 9 is the exterior angle. The other two marked angles are interior angles. They are, moreover, "remote interior angles" because they are away from the exterior angle.
So here's how to set up an equation:
the two remote interior angles added together equal the exterior angle.
2x + 3x - 12 = 4x + 9
Combine like terms.
5x - 12 = 4x + 9
Subtract 4x
x - 12 = 9
Add 12
x = 21
The exterior angle is:
4x + 9
= 4(21) + 9
= 84 + 9
= 93