Human: Harry's birthday was three weeks after the closing of the school. His three friends decided to contribute an equal amount of money to throw him a party. Harry added $30 to the contribution, making the total contribution three times as much as Harry contributed. Calculate the total amount of money that each of Harry's friends contributed. Assistant: 
How much money did Harry's friends contribute? ** If the total contribution was three times as much as Harry contributed, and Harry contributed $30, the total contribution was 3*$30=$<<3*30=90>>90
How much money did Harry's friends contribute? ** Since Harry contributed $30, his three friends together contributed $90-$30=$60
How much money did each of Harry's friends contribute? ** Since the three friends were contributing an equal amount, each friend contributed $60/3=$<<60/3=20>>20.
#### 20