Explanation: To estimate the sum of these numbers, simply add the whole numbers of 9 and 1: 9 + 1 = 10 and then judge what the fractions will add up to roughly. 12/15 is almost 1, and it is more than 1/2, so it will round up to 11.
But to be sure you can check: 9 12/15 + 1 2/6 9 24/30 + 1 10/30 = 10 34/30 = 11 4/30 = 11 2/15
Since there is no base down payment or anything the equation i think would just be 35m = c If there was say a one time payment of $20 and then the monthly payments it would look like 20+35m=C I hope this helps :)
