Find the measure of the exterior angle.

138°

Step-by-step explanation:

An exterior angle has the same measure as the sum of the two opposite interior angles. Insert the two given interior angles as the sum of the exterior angle:

Simplify the equation. Solve for x, then insert the value of x into the value of the exterior angle.

Simplify parentheses:

Combine like terms by addition or subtraction as necessary:

Get the variables on the same side. Use inverse operations. Subtract x from both sides:

The value of x is 69. Insert into the value of the exterior angle*:

Simplify:

The measure of the exterior angle is 138°.

:Done

*You can also insert the value of x into (x+9) and then add the simplified value to the other interior angle, 60:

36

step-by-step explanation: