Answer: 25.9
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x = length of AB
The parallel bases of the trapezoid can be added up, and divided over 2, to get the length of the midsegment. The midsegment is the line that cuts the nonparallel sides (or legs) of the trapezoid in half. The midsegment is parallel to the bases.
So,
(AB+DC)/2 = MN
(x+11.5)/2 = 18.7
x+11.5 = 2*18.7
x+11.5 = 37.4
x= 37.4-11.5
x = 25.9
AB = 25.9
