You will receive a free beverage and free desert on your 60th visit.
Beverage- 1, 2, 3, 4, 5, 6
Visits- 12, 24, 36 ,48 ,60
Desert- 1, 2, 3 ,4
Visits- 15, 30, 45, 60
Notice how for beverages at 60 visits you get your 6th drink for free, and for deserts, at you 60 visits you receive your 4 free desert.
So, since both numbers have the same number (60) of visits which is their common multiple between the 2, you answer is 60.
