Find three pairs of numbers for which the LCM (least common multiple) is the product of the two numbers;

Question

The pairs and LCMs are:
8 and 12: 24; 3 and 15: 15; 7 and 11: 77; 9 and 10: 90; 24 and 36: 72; 20 and 25: 100; 14 and 42: 42; 30 and 12: 60

Answer 1

The LCM is the product if they have no factors in common (relatively prime)

Now it should be easy to pick the proper pairs.

In fact, since they actually gave you the LCM's, it's just a matter of seeing whether the two numbers multiply to give the indicated LCM!