A train has 18 carriages (including the front of the train). When eating at noon, the chef found that the possibility of passengers coming to eat from the rear of the train is three times that of the front of the train. So the dining car is from the front to the train. What car is it in the rear direction? (Except for the locomotive, the number of passengers in each car to the dining car is the same)
一列火车共有18节车厢(含车头)，中午用餐时，厨师长发现，前来用餐的乘客从车尾方向来的可能性是从车头方向来的可能性的3倍，那么餐车是车头到车尾方向的第几节车厢？(除火车头外每节车厢到餐车用餐的乘客人数相同)
<gadget id="calculator">18 - 1 - 1</gadget>
<output>16</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

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

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

<result>5</result>