Please help me i dont get it

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.

Explain how you can use the associative property to evaluate (7x50)x4.

Ahiker stands at an unknown elevation before he ascends 2 miles up a mountain to an elevation of 9 miles. find the elevation of the hiker before his ascent.