Add 2.4 to the former term of 4:15, in order to keep the obtained ratio unchanged, how much should be added to the latter term of the ratio.
把4：15的前项加上2.4，为了要使所得的比值不变，比的后项应加上多少．
<gadget id="calculator">24 - 15</gadget>
<output>9</output>

<result>9</result>