Answer:
14 inches
Step-by-step explanation:
The volume of a rectangular prism is V=l*w*h
Given the info in the problem, we have:
840=l*10*6
840=60l
14=l
The length of the prism is therefore 14 inches because volume is length*width*height and since we already have the volume, height, and width, we need to get the variable for length by itself.