Emma has $26 for her weekend expenses. She spent $12.81, including tax, on a new book. Additionally, she needs to set aside $10.00 for a lunch outing next week. If stickers cost $0.42 per package, tax included, describe the maximum number of packages (p) Emma can buy.
Emma has $26 - $12.81 = $<<26-12.81=13.19>>13.19 left after buying the book.
After setting aside money for her lunch outing, she has $13.19 - $10.00 = $<<13.19-10=3.19>>3.19 left.
She can buy a maximum of $3.19 / $0.42 = <<3.19/0.42=7.60>>7.60 packages of stickers.
Since she cannot buy a fraction of a package, the maximum number of packages she can buy is 7. Answer: \boxed{7}.