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? Let's answer step by step:
John earnt $18 / 2 = $9 on Sunday. In total, John made $18 + $9 + $20 = $47 over the two weekends. John needs $60 - $47 = $13 extra to buy the pogo stick. The answer: 13.