You are given a math word problem and you are supposed to apply a single mathematical operator like addition, subtraction, multiplication, or division on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
Q: alyssa has 30 books in her library . she bought several books at a yard sale over the weekend . she now has 88 books in her library . how many books did she buy at the yard sale ?
A: 
58