Wang Lei brought 100 yuan to buy stationery. She used up (1/2) to buy pens and the rest (2/5) to buy exercise books. How much money does she have left?
王蕾带了100元钱去买文具，她买笔用去了(1/2)，买练习本花了剩下的(2/5)，她还剩多少钱？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) * (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">100 * (3/10)</gadget>
<output>30</output>

<result>30</result>