In the aircraft model interest group, males accounted for the whole group (4/7), and then 2 males were added, and the number of males at this time was exactly the current total (3/5). How many people were there in the original group?
航模兴趣小组原来男生占全组人数的(4/7)，后来又增加2名男生，这时男生人数正好是现在全组的(3/5)．原来全组有多少人？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) / (2/5)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 - (4/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(4/7) / (3/7)</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">(3/2) - (4/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">2 / (1/6) / (3/7)</gadget>
<output>28</output>

<result>28</result>