There are 4 classes in the fourth grade, with an average of 45 students in each class. Among them, there are 42 students in the first class, 48 students in the second class, 44 students in the third class, and how many students are in the fourth class.
四年级有4个班，平均每班45人，其中一班有42人，二班有48人，三班有44人，四班有多少人．
<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">180 - 42 - 48 - 44</gadget>
<output>46</output>

<result>46</result>