Samir knows that the volume of prism is 40 cubic units . he also knows that the width can of the prism is 2 units and the height is 5 units. what is the length of the prism?

Assuming this a rectangular prism, we will use the formula V=lwh to help us.  V stands for Volume, l is the length, w is the width, and h is the height.  If we know the Volume is 40 cubic units and the width is 2 units and the height is 5 units, we will put in the formula what we know.  40 cubic units = length times 2 units times 5 units.  To find the missing factor, we will divide 40 by 10 (2 times 5).  This gives us a length of 4 units.