I need help doing this it’s the homework but I need to understand it for the test

By similar triangle, we have:
[tex]\begin{gathered} Let\text{ the unknown measurement be x} \\ \text{Thus, we have:} \\ \frac{14}{x}=\frac{8}{15} \\ \text{cross}-\text{multiply} \\ 8x=210 \\ x=\frac{210}{8} \\ x=26.25\text{ f}eet \end{gathered}[/tex]Hence, the unknown measurement of the plan is 26.25 feet