A row of trees is planted on the side of an 85-meter-long avenue at the school gate. The starting point and the ending point are planted. A total of 18 trees are planted. The distance between two adjacent trees is equal. Find the distance between two adjacent trees.
校门口一条长85米的林阴道一旁栽了一行树，起点和终点都栽，一共栽了18棵，相邻两棵树之间的距离相等．求相邻两棵树之间的距离．
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">85 / 17</gadget>
<output>5</output>

<result>5</result>