Answer:B=9
Step-by-step explanation:
9 cm. It is a right triangle so you must use the Pythagorean Theorem to find the missing side: a2+ b2 = c2. You would have a2 + 122 = 152. So a2 + 144 = 225 where you subtract 144 from each side to get a2 = 81. Then you take the square root of both sides to get a = 9.