Add 15 to the former term of 3:5, to keep the ratio unchanged, how much should the latter term be multiplied by.
3：5的前项加上15，要使比值不变，后项应乘以多少．
<gadget id="calculator">3 + 15</gadget>
<output>18</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<result>6</result>