You can put this solution on YOUR website! .05(x+20)+.40x=4.15
x=7 number of books bought.
7+20=27 pamphlets bought.
Let represent the number of pamphlets purchased. Then must represent the number of books purchased.
Each pamphlet costs 5 cents, so the total amount paid for pamphlets must be cents. Each book costs 40 cents, so the total amount paid for books must be . And the sum of these two amounts is $4.15, which we can represent at 415 cents so that the units of measure are consistent. (alternatively, you could say that the total cost of pamphlets was and the total cost of books and then the sum would be 4.15, but I just like to work with integer coefficients)