In order to find the length of the third side, since we have a right triangle, we can use the Pythagorean Theorem:
[tex]\begin{gathered} 20^2=15^2+x^2 \\ 400=225+x^2 \\ x^2=400-225 \\ x^2=175 \\ x=13.23 \end{gathered}[/tex]
Rounding to the nearest tenth, the length of the third side is 13.2 units.
