-2
the second equation is the result of subtracting 2
We start with
$1,187.92
With the interest and the late fee charge
$1,187.92 (1 + 0.1225/12) + 30 = $1,230.05
With the interest minus the payment of $125
$1,230.05 (1 + 0.1225/12) - $125 = $1,117.60
The new principal after the latest payment is $1,117.60.
B.
He has used the highest recommended percentages to calculate the amounts for the three categories.
