There are 3 classes in the fourth grade with an average of 45 students in each class. There are 47 students in the first class and 45 students in the second class. How many students are there in the third class?
四年级3个班平均每班有45人，其中一班有47人，二班有45人，则三班有多少人．
<gadget id="calculator">45 * 3</gadget>
<output>135</output>

<gadget id="calculator">47 + 45</gadget>
<output>92</output>

<gadget id="calculator">135 - 92</gadget>
<output>43</output>

<result>43</result>