Add a restaurant after every 12 visit you receive a free beverage after every 15 where is it you receive a free dessert which visit will you first receive a free beverage and a free desert

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.