Answer:
MK
Step-by-step explanation:
ML is the short side of right triangle MLK. MJ is the hypotenuse of right triangle MKJ. This gives you a clue that the ratios of interest are the short side to the hypotenuse. All these right triangles are similar, so ...
ML/MK = MK/MJ . . . . . ratio of short side to hypotenuse is the same
ML·MJ = MK² . . . . . . . cross multiply
MK = √(ML·MJ) . . . . . the geometric mean of ML and MJ is MK
