8:7=24:21, if the inner item 7 is increased by 7, how much the outer item 8 should be increased is a ratio.
8：7=24：21，如果内项7增加7，外项8应增加多少还是比例．
<gadget id="calculator">7 + 7</gadget>
<output>14</output>

<gadget id="calculator">14 * 24</gadget>
<output>336</output>

<gadget id="calculator">336 / 21</gadget>
<output>16</output>

<gadget id="calculator">16 - 8</gadget>
<output>8</output>

<result>8</result>