There are 60 students in Class 1, the number of boys is the whole class (7/12), and after a few girls are transferred, the number of boys is the whole class (5/9). How many girls are transferred?
六1班有学生60人，男生人数是全班的(7/12)，又转来几名女生后，这时男生人数是全班的(5/9)．又转来几名女生？
<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">(7/12) / (5/9)</gadget>
<output>21/20 = around 1.05</output>

<gadget id="calculator">60 * (21/20)</gadget>
<output>63</output>

<gadget id="calculator">63 - 60</gadget>
<output>3</output>

<result>3</result>