The ratio of the side lenghths of two cubes is 3:7. find the ratio of their volumes

27:343 because since the side lengths are like cm or in, it's always to the power of 1, but it is invisible, so since you want to know the ratio of the volume, volume is always inches cubed or centimeters cubed etc. So you get the original ratio of the side lengths to the first power, and do each number to the third power which gives you that ratio.