Answer: 12 centimeters
Explanation:
We can use the pythagorean theorem to solve this problem. The pythagorean theorem is a^2+b^2=c^2 (where a and b are the legs and c is the hypotenuse). We can plug in 15 for c and 9 for a which gives us 9^2+b^2=15^2. We can then solve this and get 81+b^2=225 and b^2 = 144. b=12