Geometry

Question Analysis

This question involves the property of adjacent angles on a straight - line.

 

Key Concept Explanation

Adjacent angles formed on a straight line are supplementary, which means the sum of their measures is .

 

Step - by - Step Solution

1. Notice that the angle and the angle are adjacent angles on a straight line.

According to the supplementary - angle property, we can set up the equation .

2. Simplify the left - hand side of the equation:

Combine like terms:

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