Answer: KL = 22
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Work Shown:
The diagram is below.
In this diagram, we have KN and LM as opposite sides. For any parallelogram, the opposite sides are parallel (as shown by the arrow markers) and they are congruent to each other. In other words, KN and LM are the same length.
This means KN = LM and we can solve for x like so
KN = LM
3x-11 = x+15
3x-x = 15+11
2x = 26
x = 26/2
x = 13
Then we can find side KL
KL = 2x-4
KL = 2*13-4
KL = 26-4
KL = 22