a) The side length is 5 units since 5*5*5 = 125. You can guess and check to see which value multiplies with itself three times to get 125. Or you can take the cube root of 125 to get 5. You can type in 125^(1/3) to indicate you want the cube root of 125
b) The volume is 64 cubic units. Multiply the side length 4 by itself three times: 4*4*4 = 64.