A ratio is 2:3, if the latter term of the ratio is enlarged by 5 times, how much should the former term of the ratio be increased to keep the ratio constant.
一个比是2：3，如果比的后项扩大了5倍，要使比值不变，比的前项应增加多少．
<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">10 - 2</gadget>
<output>8</output>

<result>8</result>