what is the area of this rectangle? 21'3"x13'6" ?
First of all, convert the lengths to to a single unit.
At the moment, the lengths are in feet and inches. Convert them both to either feet or inches.
In feet, L = 21.25 ft, W = 13.5 ft, Area A = 21.25 * 13.5 = 286.875 ft^2
In inches, L = 255 in, W = 162 in, Area A = 255 * 162 = 41,310 in^2