Obviously, when doing an addition problem, I mistakenly regarded the addend 8 as 3, and the result was 42. What should be the correct result?
明明做一道加法题时，误把加数8看成了3，结果得42，正确的结果应该是多少？
<gadget id="calculator">42 - 3</gadget>
<output>39</output>

<gadget id="calculator">39 + 8</gadget>
<output>47</output>

<result>47</result>