Answer:
(c) 31 units
Explanation:
Given quadrilateral ABCD has AD║BC, with AD=3x+7 and BC=5x-9, you want to know the length of AD for the quadrilateral to be a parallelogram.
Congruent sides
Opposite sides of a parallelogram are congruent, so for ABCD to be a parallelogram, we must have ...
BC = AD
5x -9 = 3x +7
2x = 16
x = 8
AD = 3x +7 = 3(8) +7 = 31
The length of AD must be 31 units if ABCD is to be a parallelogram.
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