Try to establish a formula for B(t-1) in terms of Bo

Next, using the above and the formula B(t) = B(t-1) *(1+i) - R(t) =0 , set B(t) less than or equal to 1800

solve for t

(2) A loan of $12,500 is made at an effective interest rate of 8.5%. Payments are made at the end of each interest period. Each payment equals twice the interest due until the borrower pays off the outstanding debt with a final payment of, at most, $1,800. Find the number of payments n and the amount of the final payment