Add 16 to the former term of 4:5, and how much to add to the latter term of the ratio; the ratio remains unchanged.
把4：5的前项加上16，比的后项加多少；比值大小不变．
<gadget id="calculator">5 * 5</gadget>
<output>25</output>

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

<result>20</result>