Xiaoding has two bookshelves, the first bookshelf is 30 books less than the second bookshelf, if you take 5 books from the first bookshelf and put them in the second bookshelf, then the first bookshelf is now more than the second bookshelf How many books are missing.
小丁有两个书架，第一个书架比第二个书架少30本书，如果把第一个书架拿走5本书，放到第二个书架，那么第一个书架现在比第二书架少多少本书．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<result>40</result>