Which of the multiples of 5 that are less than 100 are also multiples of 6?
The multiples of 5 that are also multiples of 6 are multiples of
their LCM.
The LCM of 5 and 6 is 30, so the question becomes which
multiples of 30 are less than 100?
The solution is the numbers: 30, 60, 90