The Used Books Emporium is having a big sale, where the prices of all the books in stock are discounted by the same percentage. If a book that originally cost $\$15$ is now being sold for $\$4$, how many dollars will a book that was originally $\$21$ sell for? Express your answer as a decimal.

5.60

Step-by-step explanation:

Let p equal the new price, in dollars, of the book that originally cost $21. Since we know that the prices of both books are discounted by the same percentage, we can set up the ratio p/21 =4/15

So,

p= 4/15*21

and p=5.60

48 / 6 = x

in this case, x will equal the amount of money in each card!

x therefore will be 8.

trent had $8 in each birthday card.