well, we know the cash price, that is, if you have cash burning your pockets, is R6900 bucks, however you'd rather do it in installments, or hire purchase with a downpayment of 15% of 6900, hmmm how much is that?

now, to that downpayment let's add the 12 installments of R558.50

ohhh man!!! you ended up paying 7737 - 6900 = 837 more on hire purchase.