A sealed box contains 4 red balls, 5 yellow balls, and 7 white balls. Xiaolin reaches out and grabs a ball at random. The chance of catching a red ball is ((())/(())).
一个密封的箱子里装有红球4个，黄球5个，白球7个，小林伸手任意抓了一个球，抓到红球的机会是((())/(()))．
<gadget id="calculator">4 + 5 + 7</gadget>
<output>16</output>

<gadget id="calculator">4 / 16</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>