How many boats have been rented by the students for the spring outing? If each boat takes 3 people, there will be 16 people without a boat. If each boat takes 5 people, there will be 4 people in 1 boat.
同学们春游租了几条船，如果每条船坐3人，就有16人没船划，如果每条船坐5人，则有1条船差4人，问一共租了几条船？
<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>