In the ratio 5:3=15:9, if the inner term 3 increases by 3, how much should the outer term 5 increase.
在比例5：3=15：9中，如果内项3增加3，外项5应该增加多少．
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

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

<gadget id="calculator">90 / 9</gadget>
<output>10</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>