Unexpected symbol 'Instantiate' [SOLVED]

I'm still new at c# and don't know anything much yet, and I have facing this error saying : 'Unexpected symbol 'Instantiate'

Here's my entire code for now

 using UnityEngine;
 using System.Collections;
 
 public class Move : MonoBehaviour {
     public float postx = 0;
     public float posty = 0;
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         float posty = transform.position.y;
         float postx = transform.position.x;
     }
 
     
     void show(){
         Vector3 post = new Vector3(postx + 10f, 0 , Random.Range(posty + 10f, posty - 10f))
         Instantiate(prefab, post, Quaternion.identity) as GameObject;
         
     }
 }

could you help me find where did I doing wrong please ? Thanks in advance...