There are 3 classes in the second grade with an average of 40 students in each class, 38 students in Class 1, 40 students in Class 2, and how many students are there in Class 3.
二年级3个班平均每班有40人，1班有38人，2班有40人，3班有多少人．
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">38 + 40</gadget>
<output>78</output>

<gadget id="calculator">120 - 78</gadget>
<output>42</output>

<result>42</result>