If the former term of 4:5 is increased by 16, how much should the latter term be increased to keep the ratio constant
如果4：5的前项增加16，要使比值不变，后项应增加多少
<gadget id="calculator">4 + 16</gadget>
<output>20</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<result>20</result>