52 students go rowing in the park. Each large boat can seat 8 people, and each small boat can seat 4 people. After calculation, the 9 boats are exactly full. How many large boats do you need to rent?
52名学生去公园划船，大船每条可坐8人，小船每条可坐4人，经计算，乘坐9条船正好坐满，大船要租多少条．
<gadget id="calculator">9 * 8</gadget>
<output>72</output>

<gadget id="calculator">72 - 52</gadget>
<output>20</output>

<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<result>4</result>