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Explanation:
If you have n sides of a polygon, then the interior angles add up to S = 180(n-2)
In this case, n = 5, so S = 180(n-2) = 180(5-2) = 540
We can add up the five angles the diagram shows and set that sum equal to 540 to solve for x
S+T+U+V+W = 540
90+2x+x+2x+90 = 540
5x+180 = 540
5x = 540-180
5x = 360
x = 360/5
x = 72
Since angle U = x, this means angle U = 72 degrees