Mr. Li bought 20 boxes of ballpoint pens, and the number of pens he bought was less than that of ballpoint pens (2/5). How many boxes of pens did he buy?
李老师买来20盒圆珠笔，买来的钢笔比圆珠笔少(2/5)，买来钢笔多少盒？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">20 * (3/5)</gadget>
<output>12</output>

<result>12</result>