Draw the situation for a better understanding:
To find the height at which the top of the ladder reaches the wall use pythagorean theorem:
[tex]\begin{gathered} h=\sqrt[]{13^2-5^2} \\ h=\sqrt[]{169-25} \\ h=\sqrt[]{144} \\ h=12 \end{gathered}[/tex]
The height at which the top of the ladder reaches the wall is 12 ft.
