First, you need to look for the width of the parallelogram because you already know the length which is 20.5 in
Given that 50.5 in wide and the gap in between each measures 4.25 in.
There are two gaps so 2 × 4.25 = 8.5 in
Subtract this from the total width of 50.5 in so that you're only left with the real measures for the width of the three parallelogram
50.5 - 8.5 = 42 inches
The total width of the three parallelogram without the two gaps is 42 inches.
Divide this in three so that you're left with the width for only one parallelogram.
42 ÷ 3 = 14 inches
Now the length is 20.5in and the width is 14 in.
The area formula is A = l × w
A = 20.5 × 14
A = 287 square inches