Finding unknown variables
Values
Subscription: $5.95 per month
One print: $0.19
January charge: $15.83
Number of prints: ?
Procedure
We need to know the amount of money of the January charge that correspond to the prints. Since it has two components (subscription and prints), we find that value substracting
$15.83 - $5.95 = $9.88
We find the number of prints dividing that value into the cost of each print
$9.88/$0.19 = 52
Answer: D (52 prints)