The sports group has a basket of balls, of which footballs account for 9/20. If 5 more basketballs are put in, footballs only account for 9/25. Then, how many footballs are there in this basket?
体育组有一筐球，其中足球占9/20，如果再放入5个篮球，足球就只占9/25，那么，这筐球中，足球有多少个．
<gadget id="calculator">25 - 9</gadget>
<output>16</output>

<gadget id="calculator">16 / 9</gadget>
<output>16/9 = around 1.777778</output>

<gadget id="calculator">20 - 9</gadget>
<output>11</output>

<gadget id="calculator">11 / 9</gadget>
<output>11/9 = around 1.222222</output>

<gadget id="calculator">(16/9) - (11/9)</gadget>
<output>5/9 = around 0.555556</output>

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

<result>9</result>