IF LOAN BALANCE IS 34,000.00 AND YOU PAY $597.21 MONTHLY AT 7.50 INTEREST HOW MUCH TIME WILL YOU CUT OFF TERM OF LOAN IF YOU ADD 100.00 TO MONTHLY PAYMENT

original plan:

payment = 597.21
i = .075/12 = .00625
n = ?

34000 = 597.21 (1 - 1.00625^-n)/.00625
.3558212.. = 1 - 1.00625^-n
1.00625^-n = .644178764
-n(log 1.00625) = log .64417..
-n = -70.58
n = 70.58 months

new plan:
payment = 697.21

everything stays the same,
repeat the above steps to find the new n value