of the given interior angles and set the sum equal to 540". mZA + 105° + 102° + 75° + 90° = 540° mZA + 372° = 540° Combine like terms. Subtract 372" from each side. b. The polygon has 7 sides, so the sum of the measures of the interior angles is: (n-2)180° = (7 - 2)180° = 5(180°) = 900°. Add the measures of the given interior angles and set the sum equal to 900°. MZA+ 128° + 131° + 125° + 127° + 94° + 125º = 900° MZA + 730º = 900° MZA = 170° Thus, mZA is 170°. E CHECKPOINT 2: Find the measure of ZA in the figure on the right. D 1121 125 118 F cu С 152 182 A B LESSON 3: Sides of a Polygon​