Answer:
B. 120°
Step-by-step explanation:
Sum of the measures of the interior angle of a polygon with n sides:
(n - 2)180
We have a pentagon, a 5-sided polygon, so n = 5.
We first find the sum of the measures of the angles of any pentagon.
(5 - 2)180 = 3(180) = 540
From the figure, we add the measures of the 5 angles and set the sum equal to 540°.
3x + 4x + 4x + 4x + 3x = 540°
18x = 540°
Divide both sides by 18.
x = 30°
The angle at vertex C measures 4x.
4x = 4 * 30° = 120°
Answer: B. 120°
