i want to be able to go back to the main menu from my game

it always comes up with this error

Assets/scripts/leave.cs(16,13): error CS0131: The left-hand side of an assignment must be a variable, a property or an indexer

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

public class leave : MonoBehaviour {

	void Update () 
	{
	

	if (Input.GetKeyDown (KeyCode.Escape) = Application.LoadLevel (0)) {

	}
}

}

using UnityEngine.SceneManagement; // at the top

  void Update(){     
 if (Input.GetKeyDown (KeyCode.Escape))
{
SceneManager.LoadScene (0);
}
}