There are 48 students in class 3, and girls account for the whole class (1/12). After transferring a few girls, girls account for the whole class (1/5).
六3班有48人，女生占全班的(1/12)，转来多少名女生后，女生占全班的(1/5)．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 - (1/12)</gadget>
<output>11/12 = around 0.916667</output>

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

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(11/12) / (4/5)</gadget>
<output>55/48 = around 1.145833</output>

<gadget id="calculator">48 * (55/48)</gadget>
<output>55</output>

<gadget id="calculator">55 - 48</gadget>
<output>7</output>

<result>7</result>