What is the volume of a rectangular prism measuring 12 inches by 7 inches by 4 inches?

There are infinitely many possibilities.

Select any positive numbers x and y and let z = 12/(x*y)

Then a rectangular prism with sides measuring x, y and z feet will be

x * y * 12/(x*y) = 12

Since the only restriction on x and y was that they were positive numbers there are an infinite number of choices for each.

So, if x = 10 ft, y = 32 ft then z = 12/320 = 0.0375 ft = 0.45 inches.