Answer: 15 yards
Step-by-step explanation:
Using the Pythagorean Theorem, a^2+b^2=c^2, where a and b are the side lengths of the legs, and c is the length of the hypotenuse. Plugging in your values,
12^2+9^2=c^2
144+81=c^2
225=c^2
[tex]\sqrt{225}=\sqrt{c^{2} }[/tex]
15=c