Answer :
Start: 35 stickers; stickers are given to 3 friends, each have an equal amount.
1st Change: 20 are left; 35-20=15 stickers lost; 15/3= 5; the three friends got 5 stickers each.
2nd Change: 20 stickers, 5 friends. Each friend gets an equal amount. (20/5=4) 4 stickers were given to the 5 friends.