We can write an equation for the length in terms of the width here and use that to solve the problem:
[tex]l=\frac{3}{2}w-3[/tex]
Now substitute in the information that we know, namely [tex]l=123[/tex]:
[tex]123=\frac{3}{2}w-3[/tex]
[tex]126=\frac{3}{2}w[/tex]
[tex]84=w[/tex]
So the width is 84 feet.
