We know that
• The area of the land is 240 square feet.
,
• The length of one side is 15 feet.
To find the width, we have to use the area formula for rectangles.
![A=wl](https://img.qammunity.org/2023/formulas/mathematics/high-school/jw1tiv8yl5al1lvyyixox3n0s2pe0v9x2j.png)
Replacing the given information, we have
![\begin{gathered} 240=w(15) \\ w=(240)/(15)=16 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/mxtama67uos50dq6ofvdnbs6kxnr692uo9.png)
Therefore, the width of his future garden will be 16 feet long.