What is %90, percent of 20?

An animal shelter has 21 puppies. if the puppies are 28% of the total dogs and cat population how many dogs and cats are in the animal shelter

Simplify (a/b - b/a) times (a - a^2/a+b) a - a^2/a=b is a mixed number

Marla bought a book for $12.95, a binder for $3.49, and a backpack for $44.99. the sales tax rate is 6%. find the amount of tax and the total she paid for these items