The sum of three numbers is 123.5, the first addend is 23.5, the second addend is 12.5, what is the third addend.
三个数的和是123.5，第一个加数是23.5，第二个加数是12.5，第三个加数是多少．
<gadget id="calculator">23.5 + 12.5</gadget>
<output>36</output>

<gadget id="calculator">123.5 - 36</gadget>
<output>87.5</output>

<result>87.5</result>