The correct pair is 15 and 20
Here, we want to select the pair of numbers which 60 is their LCM
What this mean is we want to select two numbers that 60 is the smallest multiple they have
For 12 and 18, the lcm is 36; so this is incorrect
For 10 and 30, the lcm is 30; so this is also incorrect
for 20 and 25, the lcm is 100; this is also incorrect
for 15 and 20, the lcm is 60 and this is our correct choice
