Since 3 and 6 are factors of 24, then the LCM of either of them and 24 can’t be 72. We can rule out A and B as the correct answer. Now let’s look at 9. Since 9 = 3^2 and 24 = 3 x 2^3, the LCM of 9 and 24 is 3^2 x 2^3 = 8 x 9 = 72. Since 9 is a factor of 54, the GCD of 9 and 54 is 9. So z must be 9.
Answer: C
