Given:
total cost= $720
length=15 feet.
cost of per square feet=$4
let width of room is= x
then area of room is:
[tex]\begin{gathered} \text{Area}=\text{length}\times\text{width} \\ \text{Area}=15\times x \\ =15x \end{gathered}[/tex]if the cost is $4 per square feet then total cost in room is:
[tex]\begin{gathered} \cos t=4\times15x \\ =60x \end{gathered}[/tex]the given total cost is $720 then width of room is:
[tex]\begin{gathered} 60x=720 \\ x=\frac{720}{60} \\ x=12 \end{gathered}[/tex]so width of room is 12 feet.
