Increase the former term of 7:10 by 10.5, to keep the ratio unchanged, how much should the latter term be increased.
把7：10的前项增加10.5，要使比值不变，后项应增加多少．
<gadget id="calculator">7 + 10.5</gadget>
<output>17.5</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">17.5 / (7/10)</gadget>
<output>25</output>

<gadget id="calculator">25 - 10</gadget>
<output>15</output>

<result>15</result>