James has 28 marbles.  He puts them into 4 bags.  He puts the same number in each bag.  He then gives one bag away.  How many marbles does James have left?
James has 28 marbles / 4 bags = <<28/4=7>>7 marbles per bag.
James has 28 marbles - 7 marbles = <<28-7=21>>21 marbles remaining.
#### 21