After 6 meters of a rope are used up, there is still (2/5) left. If (7/10) is used up, how many meters are left.
一根绳子用去6米后，还剩(2/5)，如果用去(7/10)后，还剩多少米．
<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">6 / (3/5)</gadget>
<output>10</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

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

<result>3</result>