Question

I have to find the portion of the distance "x" of hypotenuse, of a right triangle with one leg equal 18, a circle inside the triangle with a radius of 5. There's a letter "C" inside the circle. Also, the teacher said to put the letter "C", down by the leg with the value of 18. I have no other information. The distance "x" is not specified as anything. It's just a portion of the hypotenuse! Help!!!