Answer:
A. x = 4
B. ∠C = 80°
Step-by-step explanation:
A.
The sum of interior angles in a pentagon is 540°. We can write an equation for the sum of angles using this fact. Clockwise from lower left, we have ...
140° +(20x)° +100° +(16x +16)° +(160 -5x)° = 540°
31x +416° = 540° . . . . . . collect terms
31x = 124° . . . . . . . . . . subtract 416°
x = 4
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B.
The measure of angle C is found by substituting the value of x into the given expression for angle C.
(16x +16)° = (16(4) +16)° = 80°
Angle C is 80°.
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Additional comment
It can be useful to remember that the sum of interior angles of an n-gon is ...
(180°)(n -2)
This can be derived from the fact that the sum of exterior angles is always 360°.
These relations apply to convex polygons. YMMV when there are reflex angles or when sides cross each other.
