Answer: There are 375 star stickers and 125 heart stickers.
There are 500 stickers with 20 stickers per sheet; 500/20 = 25 sheets of stickers.
25% of each sheet is hearts; 25/100(20) = 5 heart stickers per sheet. 5(25) = 125 total heart stickers.
20 stickers per sheet - 5 heart stickers per sheet = 15 star stickers per sheet. 15(25) = 375 total star stickers.