get 30 pennies make 3 rows of ten now take 5 away how many r in each row now??8, 8, 9 now give back 3 pennies u now have 9,9 10 in each row. thats 28 plus your 2 makes 30.you made them pay 2 dollars more than the 25 dollar bill(.if you would of gave them the 2 dollarsback then they would of...