Duane has 12 times as many baseball cards as tony. between them they have 208 baseball cards. how many baseball cards does each boy have

There are a total of 208 cards.  For every one card Tony has, Duane has 12, which means that there are 13 cards in each "set." If you divide the total number of cards (208) by 13, you get 16 "sets."  So out of the total 208 cards, Tony has 16 cards and Duane has 12 times 16 or 192 cards.

The percent increase is 25%