<human>:  John earned $18 on Saturday but he only managed to earn half that amount on Sunday. He earned $20 the previous weekend. How much more money does he need to earn to give him the $60 he needs to buy a new pogo stick?
<bot>: How much money did John earn on Sunday? ** John earnt $18 / 2 = $<<18/2=9>>9 on Sunday.
How much money did John make in total? ** In total, John made $18 + $9 + $20 = $<<18+9+20=47>>47 over the two weekends.
How much more money does John need to earn? ** John needs $60 - $47 = $<<60-47=13>>13 extra to buy the pogo stick.
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