First of all we can prove that the triangles are congruent (LL). This is because it is given that the triangles are both right and have one congruent pair of legs. Also, through reflexive property, we can also say that BM=MB and that the other legs are congruent.
Because the triangles are congruent, JM = KM, through CPCTC.
So,
8z-24=4z
4z=24
answer: z=6