Answer:
15.6
Explanation:
Because it is a right triangle, you can use the Pythagorean Theorem. The theorem is c^2 = a^2 + b^2, with c being the hypotenuse, and a and b being the legs. So plug in the values and you will get 18^2=9^2 + b^2. Solve for b and you will get 15.6.