When dealing with added tax you're going to want to turn the percentage into a decimal which will make things a lot easier. 8% is going to be .08. When you turn the percentage into a decimal you want to multiply 325 by .08, this will tell you how much tax is being paid. 325 * .08 is 26, now all you have to do is add 26 to the original price and you'll have the final price which is 351.
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 :)
