Final answer:
The perimeter of the sheetrock is 20 feet.
Step-by-step explanation:
To find the perimeter of a rectangle, we need to add up the lengths of all its sides.
In this case, we have a rectangular piece of sheetrock with a length of 7 feet and a width of 3 feet.
The formula for the perimeter of a rectangle is P = 2L + 2W, where P is the perimeter, L is the length, and W is the width.
Plugging in the values, we get P = 2(7) + 2(3) = 14 + 6 = 20 feet.