There are some books on Xiao Ming's bookshelf, the number of books is between 100-150, among which (3/7) are story books, (3/20) are science and technology books, how many books can be placed on the bookshelf at most.
小明的书架上放着一些书，书的本数在100-150本之间，其中(3/7)是故事书，(3/20)是科技书，书架上最多放着多少本书．
<gadget id="calculator">20 * 7</gadget>
<output>140</output>

<result>140</result>