There are 20 mathematics books and some language books on the bookshelf. If you take a book from the bookshelf at random, the possibility of getting a mathematics book is high. So how many mathematics books are there at least?
书架上有数学书和一些语文书共有20本，如果任意从书架上拿一本书，拿到数学书的可能性大，那么数学书最少有多少本．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>