Answer:
(7x + 10y)
Step-by-step explanation:
To find this add (3x - 4y) to itself to calculate to lengths of the shorter sides.
(3x - 4y) + (3x - 4y) = 6x - 8y
Subtract this from (20x + 12y)
(20x + 12y) - (6x - 8y) = 14x + 20y Divide this by two to get the length of one side
14x + 20y / 2 = 7x + 10y
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