Answer:
12' 1" 3/4 x 21' 1" 3/4
Explanation:
We simply have to calculate the interior dimensions.
We'll assume there's a wall all around the area, so to calculate the inner space, we have to subtract the wall's thickness from the given dimensions... twice, since there's a wall at both ends of the width and both ends of the length.
Width: 13' - 5" 1/8 - 5" 1/8 = 13' - 10" 2/8 = 12' 1" 6/8 = 12' 1" 3/4
Length: 22' - 5" 1/8 - 5" 1/8 = 22' - 10" 2/8 = 21' 1" 6/8 = 21' 1" 3/4