The three classes of the third grade have an average of 45 students in each class, including 42 students in the first class, 46 students in the second class, and how many students in the third class.
三年级3个班平均每班有学生45人，其中一班42人，二班46人，三班多少人．
<gadget id="calculator">45 * 3</gadget>
<output>135</output>

<gadget id="calculator">42 + 46</gadget>
<output>88</output>

<gadget id="calculator">135 - 88</gadget>
<output>47</output>

<result>47</result>