Amount used from credit card = $1900
Rate of interest for 12 months = 30%
a- What percentage will be charged each month?
He will be charged
% every month.
b- ) What will be the interest charge for the first month?

=
(1 month is taken as
)
$47.50
He will be charged $47.50 in interest for the first month.
c) What is his balance after making a $100 payment?
Let us assume that Billy paid $100 after 1st month. So after 1st month the amount due is 1900+47.5= $1947.50
Billy paid $100 from 1947.50, so balance remains = 1947.50-100= $1847.50
d) What is the interest charge for the second month?
Now interest charge will be calculated on 1847.50
interest =

= $ 26.39 or rounding it off we get $26.40.