Girls accounted for (2/5) of a science and technology invention interest group, and 15 girls were transferred later. At this time, girls accounted for the total number (3/5). How many boys are there in this interest group?
某科技发明兴趣小组中女生占(2/5)，后来又转来了15名女生，这时女生占总人数的(3/5)，这个兴趣小组男生有多少人？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">15 * (3/5)</gadget>
<output>9</output>

<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5) - 1</gadget>
<output>-4/5 = around -0.8</output>

<gadget id="calculator">1 + (-4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">6 / (1/5)</gadget>
<output>30</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">30 * (3/5)</gadget>
<output>18</output>

<result>18</result>