Answer: x = 40
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Work Shown:
Straight lines DF and EC intersect at point A. Because of this, angle DAF is a 180 degree angle.
Angles DAB, BAC, and CAF all combine to form a straight 180 degree angle.
Add up the angles mentioned, set the sum equal to 180, and solve for x
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(angle DAB) + (angle BAC) + (angle CAF) = 180
x + 80 + 60 = 180
x + 140 = 180
x + 140-140 = 180-140 ... subtract 140 from both sides
x = 40