Abathtub is in the shape of a rectangular prism. its dimensions are 5 feet by 3 feet by 18 inches. the bathtub is three-fourths full of water and drains at a rate of 1 cubic foot per minute. about how long does it take for all the water to drain?

The bathtub has dimensions 5 ft by 3 ft by 18 inches.
Note that 18 inches = 18/12 = 1.5 ft.

The volume of the bathtub is
V = 5*3*1.5 = 22.5 ft³

The bathtub is three-fourths (0.75) full of water. Therefore the volume of water is
0.75*22.5 = 16.875 ft³

The water is lost at the rate of 1 ft³/min.
If it takes x minutes to empty the bathtub, then
(1 ft³/min)*(x min) = (16.875 ft³)
x = 16.875 min

16.875 minutes