4:5=8:10, if 10 is added to the last term of the first ratio, how much should be added to the last term of the second ratio.
4：5=8：10，如果第一个比的后项加上10，那么第二个比的后项应该加上多少．
<gadget id="calculator">8 * 15</gadget>
<output>120</output>

<gadget id="calculator">120 / 4</gadget>
<output>30</output>

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

<result>20</result>