Answer:
x = 12
Explanation:
In a right triangle (a triangle that has a ninety degree angle in it) the the square of the side opposite the right angle is always equal to the sum of the squares of the other two sides. Therefore, we can use the information we are given to figure out the missing side:
![15^2=225\\9^2=81\\225-81=144\\\sqrt[2]{144}=12](https://img.qammunity.org/2021/formulas/mathematics/middle-school/a9vuerexiw59g9ihjs9rcze6r8b033zeuf.png)