You have dance class every 3 days today is monday and you have dance class in how many more days will you you have dance class on monday again use the lcm to find your answer

7 days in a week, 3 days a rotation.

multiples of 7: 7, 14, 21, 28

multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24

the LCM is 21, because it is the smallest multiple of both numbers. there will be 21 more days until you take dance class on mondays.

The awnser would be : Lmc 21