Which set of ordered pairs below is a function?

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

When 142 is added to a number the result is 64 more times the number my options are 35 37 39 41

Do you mind if you guys me with this question i’m on number 8