What is the missing side length in this right triangle?

A. 15

Step-by-step explanation:

Ooh, look! This triangle is a Pythagorean triple! Without even needing to use a formula, I can tell that you are correct and the answer is A. 15.

It's based off of a 3-4-5 right triangle, because 9-12-15 simplifies to that if you divide every term by 3. It's basically just a bigger version of a 3-4-5 triangle! Isn't math cool:)

A. 15 You are correct.

Step-by-step explanation:

The formula used to find the hypotenuse in this problem is called the Pythagorean Theorum.  The formula is as follows:  a^2 + b^2 = c^2.  Or, you can say that the hypotenuse is equal to: c = the square root of a squared and b squared  added together.  This might sound confusing in the start, but here's all you have to do.  a = 9, and b = 12.  9 squared is 81.  12 squared is 144.  144 + 81 = 225.  The square root of 225 is 15, because 15 x 15 = 225.  So 15 is your answer.

step-by-step explanation: