Assume the 2018 long-term loan balance is $14,640. What excel equation would I use to predict the long-term loan balance for 2019 and 2020 with this given information?

I've used PMT function but the loan amount is coming up negative.

Assume the long term loan balance as of 2018 is amortized for 15 more years at 8%. This means that you use the loan balance in 2018 as the PV and find the payment assuming 15 annual payments at 8%. Interest in 2019 will be 8% of the 2019 loan balance; the principal paid is the payment less the interest. Do the same thing for 2020 (still 8% interest). Finding a payment on a loan is basic principles of finance material. Ask if uncertain. Assume the long term loan balance as of 2018 is amortized for 15 more years at 8%. This means that you use the loan balance in 2018 as the PV and find the payment assuming 15 annual payments at 8%. Interest in 2019 will be 8% of the 2019 loan balance; the principal paid is the payment less the interest. Do the same thing for 2020 (still 8% interest). Finding a payment on a loan is basic principles of finance material. Ask if uncertain