The problem is in the unit, how to fix it?

Question

Unity

Wrote code, gives error Assets/pers/camera.cs(24,3): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement . How to fix?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class camera : MonoBehaviour {


  public float dumping = 1.5f;
  public Vector2 offset = new Vector2 (2f, 1f);
  public bool isLeft;
  private Transform Player;
  private int lastX;



  void Start(){
    offset = new Vector2 (Mathf.Abs (offset.x), offset.y);
    FindPlayer (isLeft);
  }


  public void FindPlayer(bool PlayerIsLeft) {
    Player = GameObject.FindGameObjectWithTag ("Player").transform;
    lastX - Mathf.RoundToInt (Player.position.x);
    if (PlayerIsLeft) {
      transform.position = new Vector3 (Player.position.x - offset.x, Player.position.y - offset.y, transform.position.z);
    } else {
      transform.position = new Vector3 (Player.position.x + offset.x, Player.position.y + offset.y, transform.position.z);
    }
  }


  void Update() {
    if (Player) {
      int currentX = Mathf.RoundToInt (Player.position.x);
      if (currentX > lastX) isLeft = false; else if (currentX < lastX) isLeft = true;
      lastX = Mathf.RoundToInt (Player.position.x);

      Vector3 target;
      if (isLeft) {
        target = new Vector3 (Player.position.x - offset.x, Player.position.y - offset.y, transform.position.z);
      } else {
        target = new Vector3 (Player.position.x + offset.x, Player.position.y + offset.y, transform.position.z);
      }

      Vector3 currentPosition = Vector3.Lerp(transform.position, target, dumping * Time.deltaTime);
      transform.position = currentPosition;
    }
  }

}

PS Code for camera

Answer 1

lastX - Mathf.RoundToInt (Player.position.x);
replace with

lastX = lastX - Mathf.RoundToInt (Player.position.x);