There are 49 people in the class, boys (2/5) and girls (3/8) participated in the mathematics competition, how many people did not participate.
全班49个人，男生的(2/5)和女生的(3/8)参加数学竞赛，没参加的有多少人．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">25 * (2/5)</gadget>
<output>10</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">24 * (3/8)</gadget>
<output>9</output>

<gadget id="calculator">49 - 10 - 9</gadget>
<output>30</output>

<result>30</result>