You cannot do this as cubic feet is volume, not length. You need to know distances in three dimensions.
75 cubic feet
75 cubic feet
75000 cubic feet = 2123763 liters
75 US gallons of water equates to 10.03 cubic feet.
20 inches = 1.667 ft, cross section area = 2.183 sq ft, 75 ft long makes 163.71 cu ft
75 feet
Based on the category I am assuming we are takling dirt or mulch. 75 yds x 27 cuft (there is 27 cuft per 1 cuyd) = 2,025 cubic feet of material - 1 foot thick would be 2,025 sqft. - 6 inches thick would be 4,050 sqft. - 3 inches thick would be 8,100 sqft.
12 cubic feet. 8 x 2 x .75
75 feet,
16/0.75 = 21.33...
4200 cubic feet
The volume of the swimming pool in cubic feet would be 800 cubic feet: length x width x height = volume 10 feet x 10 feet x 8 feet = 800 cubic feet (10 x 10 = 100; 100 x 8 = 800)