Class 1, grade 4, each brought an extra-curricular book from home and set up a small library. There are 45 books in total, of which 15 are story books, 2 science books are less than story books, and the rest are all other books. Do you know how many other books there are?
四年级一班同学，每人从家里带来一本课外书，办起了小小图书室．共有45本，其中故事书15本，科技书比故事书少2本，剩下的全是其他书．你知道其他书有多少本吗？
<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<result>18</result>