they says i'm missing a semicolon at the end of line 7, I have one there already

/*1*/ var prefabBullet:Transform;

function Update () 
{
     if(input.GetButtonDown("Fire1"))
     {
/*7*/    var instanceBullet - Instantiate(prefabBullet, transform.position, Quaternion.identity);

     }
}

Try this:

var prefabBullet:Transform;

function Update ()
{ 
  if(Input.GetButtonDown("Fire1"))
  {
    var instanceBullet = Instantiate(prefabBullet, transform.position, Quaternion.identity);
  }
}