Answer:
15 feet
Step-by-step explanation:
The ladder is the hypotenuse of a right triangle, with the legs being 9 ft and 12 ft long (see the picture).
To solve for the length of the ladder, use the Pythagorean Theorem.
[tex]9^{2} +12^{2} =c^{2} \\c=\sqrt{9^{2} +12^{2}} \\c=\sqrt{81+144} \\c=\sqrt{225} \\c=15[/tex]
