i have the following model:

class Agent extends Eloquent
{
	protected $fillable = [];
	protected $table = 'agents';
	protected $primaryKey = 'id_user';
	protected $userTable = 'users';

	public function user()
	{
		return $this->hasOne('Cartalyst\Sentry\Users\Eloquent\User', 'id', 'id_user');
	}

	public function plans()
	{
		return $this->belongsToMany('Plan', 'agents_plans', 'id_user', 'id_plan');
	}

	public function promotions()
	{
		return $this->belongsToMany('Promotion', 'agents_promotions', 'id_user', 'id_promotion');
	}

	public function sales()
	{
		return $this->hasMany('Sale', 'id_user');
	}
}

how can i delete a record from one of the relational tables like agents_plans?