>>10875056TIL /sci/ is full of clueless people.
You have a right triangle with a hypotenuse of 12.
This is equivalent to saying you have an angle inscribed in a circle with a diameter of 12.
Clearly, this type of triangle works regardless of where the angle is inscribed.
Therefore, there is not enough information to answer the question, as infinite triangles with different L and H can work with the given info.
I can relate L to H if you want, but you need to give more information, such as where H intersects the length 12 line.
