Lauren wanted to make burgers and fries for dinner.  She needed a few things from the grocery store and bought the following:  2 pounds of hamburger meat that was on sale for $3.50 a pound.  1 pack of hamburger buns for $1.50.  A head of lettuce for $1.00 and a large 1.5-pound tomato that was priced at $2.00 per pound.  She also needed a jar of pickles that cost $2.50 and she had a $1.00 off coupon for that item.  How much change would Lauren get back if she paid with a $20 bill?
How to solve this?