Simon bought furniture for his apartment for a total of $2,900. The store financed his purchase for 18 months at 0% interest, and there is no minimum monthly payment amount. Simon decides to pay nothing the first month, and then $180 per month after the first month towards the total until it's paid off. Set up an equation such that Tn represents the total amount Simon still owes after n months.

Calculate the amount Simon still owes at the end of one year after his purchase.

would appreciate any help :D