Answer
Find out the length and width of the box if its volume is 768in³ .
To prove
Let us assume that the length of the rectangular solid be x .
As given
the width is three-fourths as long as the length.
Than


As given
sketchbook is 4in high .
The volume of the rectangular solid is 768 in³ .
Formula
Volume of the rectangular solid = length × breadth × height

768 = 3x²

x² = 256
As

x =16 in
Length = 16 in

= 12 in
Therefore the length and breadth of the rectangular solid be 16 in and 12 in.