It is known that the sum of two addends is 30, one of which is 13.2, and what is the other addend.
已知两个加数的和是30，其中一个加数是13.2，另一个加数是多少．
<gadget id="calculator">30 - 13.2</gadget>
<output>16.8</output>

<result>16.8</result>