Answer:6
Step-by-step explanation:
If we know that the formula of a rectangular prism is length * width * height, and we know the height and width are 7 and 9, the length is the only thing that is left. The volume is 378, and so now we have:
length * 7 * 9 = 378. Dividing the 9 and 7, we get 378/(9*7). The length is 6.
