How do you find the volume of a rectangular prism with a mixed fraction

First convert the mixed number into a improper fraction, then do length × width × hight. After covert your improper fraction back into a mixed number.

Same way you do when the sides are integers.

Example:
1 1/2 x 2 4/5 x 3 2/3 

Step 1: First you turn the mixed numbers into improper fractions. (An easy way to do that is multiply the denominator by the whole number + the numerator.)

3/2 x 14/5 x 11/3

Step 2: Then you multiply the numerators.
3 x 14 x 11 = 462

Step 3: Then you multiply the denominators.
2 x 5 x 3 = 30

Step 4: Divide the numerator by the denominator
462/30 = 15 1/5