In the English interest group of Fengfeng Primary School, boys accounted for (5/9). If 20 girls are added, boys only account for (5/13). How many boys are there in this group?
高峰小学英语兴趣小组中，男生占(5/9)，如果增加20名女生后，男生就只占(5/13)，那么这个小组中男生有多少人？
<gadget id="calculator">5 / 13</gadget>
<output>5/13 = around 0.384615</output>

<gadget id="calculator">(5/13) * 20</gadget>
<output>100/13 = around 7.692308</output>

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

<gadget id="calculator">(5/9) - (5/13)</gadget>
<output>20/117 = around 0.17094</output>

<gadget id="calculator">(100/13) / (20/117)</gadget>
<output>45</output>

<gadget id="calculator">45 * (5/9)</gadget>
<output>25</output>

<result>25</result>