this can be solve using the formula:
D = O(i)where D is the downpaymentO is the original prizei is the fraction of the downpayment
D = O(i)D = 897(0.18)D = 897(0.18)D = 161.46
so the amount he did finance is:F = 897 - 161.46F = $ 735.54 is the amount he finance