You think that Alex should ask his mum to pay by credit card. Alex has promised her that he will pay back the money next month. He will need to remember to save for this.

If Alex does not pay off the full amount on time he will have to pay more than the original price. This is interest that is calculated on a daily basis. He will end up paying back more than he borrowed if he does not pay the balance off in full. His mum could end up in debt.

Alex may want to save more first, then ask his mum to buy the tablet on her credit card, when he can pay her back faster.