Answer: x = 140 (choice C)
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Explanation:
Focus on the upper semicircle. It's composed of the arc pieces that are 30 degrees, x degrees, and y degrees. The y is the missing unmarked portion of the upper semicircle.
Subtract the 30 and y degree angles, divide by 2, and set that result equal to 10. This will help us solve for y
(30-y)/2 = 10
30-y = 10*2
30-y = 20
-y = 20-30
-y = -10
y = 10
Because the 30, x and y arcs form a semicircle, this must mean the three arcs add to 180 degrees
30+x+y = 180
30+x+10 = 180
x+40 = 180
x = 180-40
x = 140
