Help please this is so confusing

The late fee for library books is $2.00 plus 15¢ each day for a book that is late. if maria’s fee for a late book was $3.20, write and solve a linear equation to find how many days late the book was.

You earn a 12% commission for every car you sell. how much is your commission if you sell a $23,000 car?

If the discriminant if a quadratic equation is 4 which statement describes the roots?