Let x be the length and y be the width.
Then we deduce the equations :
[tex]xy=108\\ \frac{x}{y} = \frac{4}{3} [/tex]
From the first equation we get:
[tex]x = \frac{4}{3} y[/tex]
Use the value of y in the first equation like this:
[tex](\frac{4}{3} y)y=108[/tex]
Solving the above equation for y we get:
[tex]y=9[/tex] then [tex]x=12[/tex]
