Question

Spencer bought 3 books of stamps and mailed a package. it cost $4.50 to mail the package. define a variable and write an expression to represent the total amount he spent at the post office.

Answer 1

X = The cost of each book of stamps

There for your expression would be:
3x + 4.50

3x is 3 book of stamps times x cost of each book.
Your 4.50 is your one time fee to mail the package.

Hope this helps! (: