Answer:
25 feet
Step-by-step explanation:
using the sides 20 and 15, use the Pythagorean theorem to find the hypotenuse of the right triangle formed by the 2 side lengths and the diagonal.
[tex]a^{2} +b^{2} =c^{2} \\20^{2} +15^{2} =c^{2} \\400+225=c^{2} \\625=c^{2} \\25=c[/tex]