Mathematical calculation. The sum of the two numbers is 21.3, and one of the addends is 16.5. How much is the difference between these two numbers?
算式计算．两个数的和是21.3，其中一个加数是16.5．这两个数相差多少？
<gadget id="calculator">21.3 - 16.5</gadget>
<output>4.8</output>

<gadget id="calculator">16.5 - 4.8</gadget>
<output>11.7</output>

<result>11.7</result>