Xiaoqing uses some of the money (2/7) to buy a pen, and the rest (1/5) to buy a notebook, how much of the money is left.
小青用一些钱的(2/7)买钢笔，再用剩下的(1/5)买笔记本，最后还剩这些钱的多少．
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(5/7) * (1/5)</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (2/7) - (1/7)</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>