Add 10 to the outer term 5 of the ratio 5:3=10:6, how much should be added to the inner term 10 to make the ratio valid.
比例5：3=10：6的外项5加上10，要使比例成立，内项10应该加上多少．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">90 / 3</gadget>
<output>30</output>

<gadget id="calculator">30 - 10</gadget>
<output>20</output>

<result>20</result>