Answer:
x = 2(sqrt26) or x = 10.1980390272...
Explanation:
Right triangles can be solved using Pythagorean theorem, where the legs are squared and added together to get the hypotenuse's length squared.
If we set up the equation:
11^2 + x^2 = 15^2
which is
121 + x^2 = 225
subtract 121 from both sides
x^2 = 104
sqrt both sides
x = 2(sqrt26), or x = 10.1980390272...