Andy had a large collection of trading cards of famous soccer players. Many of his cards featured either Neymar (15%) or Mbappe (10%). However, Andy grew increasing discontent with Neymar’s behavior (as a “diver”) and traded all of his Neymar cards for other cards. Since Neymar cards were still quite valuable despite his antics, he managed to trade one Neymar card for 3 other cards (but none of them featured Mbappe). After the trade, what fraction of his cards feature Mbappe?
For convenience sake.....let Andy's original collection = 100 cards
So Neymar comprised 15 of these and Mbappe comprised 10
If he traded 1 Neymar card for 3 other cards, then he got rid of 15 cards and acquired 3 times this many = 45
So....now he has 100 - 15 + 45 = 130 cards
And Mbappe's cards must be 10 / 130 = 1/13 of the collection