Several students go rowing, they rent some boats, if there are 4 people in each boat, there will be 5 more people, if there are 5 people in each boat, there will be 4 vacancies on the boat. How many students are there in total?
若干个同学去划船，他们租了一些船，若每船4人则多5人，若每船5人则船上有4个空位．共有多少个同学．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">9 / 1</gadget>
<output>9</output>

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

<gadget id="calculator">36 + 5</gadget>
<output>41</output>

<result>41</result>