Hey, I am taking a Microeconomics class. A lot of the course uses this formula (that I can't figure out why I'm not grasping) and I want to make sure that I understand what I'm doing wrong and the concept of the formula before I continue without really knowing what I'm doing. --Here is the question--
Rachel is hosting the neighborhood barbecue party at her house and decides to grill hotdogs. Last year, a package of hotdog buns costed $7 and a package of hotdogs costed $10 and Rachel had bought 15 packages of buns and 15 packages of hotdogs at that time.

Now the price of buns has increased to $8 a package, and the price of hotdogs remained at $10. Rachel decides she will only buy 10 packages of hotdogs this year.

Using the mid-point formula, the cross-price elasticity is _ and the goods are _.