Step-by-step explanation: a^2 + b^2 = c^2 this is what is called the Pythagorean Theorem which means you square the two legs and then add them in this case 9 squared is 81 and 12 squared is 144 notice that when you add 144 + 81 = 225 now we just have to find the square root of 225 which is 15 because 15 times 15 is 225 so the answer is 15
