Paula purchaser borrowed $500 at 12 percent for one year. she paid a $25 processing fee.
the interest paid will be?

You will need the formula for the total loan payment.  (See attached).

rate(for this formula) = rate/1,200
n=12 months

Total = [(rate*principal)/(1-(1+rate)^-n))]*n
Total = [(.01*500)/(1-(1.01)^-12]*12
Total = [5 / (1 -0.8874492253 ] * 12
Total = [5 /  0.1125507747 ] * 12
Total = (44.4243943392) * 12
Total = 533.09
The interest is 33.09 which I'm guessing does not include the $25 processing fee.