How do you find volume when all you have is specific gravity and mass

The volume, v, of a rectangular prism is determined using the formula, where / is the length, w is the width, and his theheight of the prism. carltren solves for w and writes the equivalent equation w=using this formula, what is the width of a rectangular prism that has a volume of 138.24 cubic inches, a height of 9.6 inches,and a length of 3.2 inches?