Step-by-step explanation: The equation of the line AC is y = (-3/4)x + 12. The line perpendicular to AC and passing through point B is y = (4/3)x. The point of intersection between BK amd AC is (144/25, 192/25). Those are the side lengths. Use Pythagorean theorem to find the hypotenuse.
-3 * (-4) matches, as well as the powers (I guess you wanted to communicate that these are powers, but it would also be correct if these where factors)