This question doesn't make much sense because the length of line segments MP, PQ, and QM depend on the height of trapezoid ABCD. I'll make some changes in red ink.
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Let ABCD be a trapezoid with midsegment MN, and suppose the diagonals split MN into three segments MP, PQ, and QN. If AB = 8, CD = 12, and AD = BC = 10, find the lengths of the midsegment MN and the three segments MP, PQ, and QN.