It is known that the sum of two addends is 7.81, and one of the addends is 3.78, what is the other addend.
已知两个加数的和是7.81，其中一个加数是3.78，则另一个加数是多少．
<gadget id="calculator">7.81 - 3.78</gadget>
<output>4.03</output>

<result>4.03</result>