If line JK is tangent to the circle L, the triangle JKM is a right triangle. Then, you can calculate the line JM by using the Pythagorean theorem, as follow:
KM² = KJ² + JM²
KJ = 7
KM = 25
Solve the equation for JM and replace the values of the other parameters:
JM = √(KM² - KJ²)
JM = √((25)² - (7)²)
JM = √(625 - 49)
JM =√(576)
JM = 24
next, consider that line JM is the diameter of the circle