I tried and got the answer wrong :(

The value of the missing side of the trapezoid will be 6 inches.
A trapezoid is a quadrilateral having two parallel sides and two nonparallel sides. The area of the trapezoid is the space occupied by a quadrilateral having two parallel sides and two nonparallel sides in a two-dimensional plane.
Given that the area of the trapezoid is 21 square inches and the height is 3 inches the other side is 8 inches.
The value of the unknown side is calculated as below:-
Area = [ ( a + b ) / 2 ] x h
21 = [ ( 8 + b ) / 2 ] x 3
7 = ( 8 + b ) / 2
14 = 8 + b
b = 14 - 8
b = 6 inches
Therefore, the value of the missing side of the trapezoid will be 6 inches.
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