The remaining balance after 30 months of monthly payments of $90 is $7,336.72.
The remaining balance after 30 months is the future value of the loan.
We can compute the future value using an online finance calculator.
N (# of periods) = 30 months
I/Y (Interest per year) = 10%
PV (Present Value) = $8,100
PMT (Periodic Payment) = $-90
Results:
FV (Future Value) = $7,336.72
The sum of all periodic payments = $2,700.00
Total Interest = $1,936.72
Thus, the FV after 30 months is $7,336.72.