The problem is using a right triangle, it means we can use the Pythagorean theorem in solving the problem. We have two possible measurements for the third side.
First length, when the third side is the hypotenuse:
x ² = 15² + 12²
x = 19.21
Second possible length, when the third leg is either an adjacent or base side:
15² = x² + 12²
x = 9
Therefore, the difference between the two possible answers are shown below:
Difference = 19.21 - 9 = 10.21