Mr. Wang has to correct 48 essays. After 4 hours of correcting, there are 12 essays left. How many essays are corrected per hour on average?
王老师要批改48篇作文，批改了4小时后，还剩12篇，平均每小时批改几篇？
<gadget id="calculator">48 - 12</gadget>
<output>36</output>

<gadget id="calculator">36 / 4</gadget>
<output>9</output>

<result>9</result>