The number of passengers in a passenger car is three times that of a car. A medium-sized bus carries 16 passengers, and the number of passengers on a medium-sized bus is the sum of two passenger cars and cars. How many passengers are in the car?
小客车上的乘客人数是小轿车的3倍．中型客车载客16人，中型客车上载客数是小客车和小轿车两个的和．小轿车上有多少为乘客？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<result>4</result>