The baker is unable to fill ten platters of cupcakes without having 2 vanilla cupcakes left over. While 80 is divisible by 10 and comes out evenly, 72 on the other hand will leaving you with a decimal.
The greatest number of platters the baker can make without having any cupcakes left over are 8 platters. 8 is the greatest common factor between 80 and 72, and will give you 10 chocolate cupcakes and 9 vanilla cupcakes per platter.