Given three side length of a rectangle---0.75 feet, 9 inches, and 5 inches-- what is the length of the fourth side, in inches?
Since the first side is given in feet and the last two sides are given in inches, we need to convert the first side to inches. We know that 1 foot is equal to 12 inches, so 0.75 feet is equal to 12 * 0.75 = <<12*0.75=9>>9 inches.
Therefore, the lengths of the four sides of the rectangle are 9 inches, 9 inches, 5 inches, and 9 inches.
The length of the fourth side is 9 inches. Answer: \boxed{9}.