How do I delete this method

I can not call the methods: DeleteOnSubmit and also method: DeleteObject . See below my code and how I make a delete in it.

public static void deletaRuptura(int _idmotivo)
        {
            RupturaEntities db = new RupturaEntities();

            try
            {
                var monta_arvore = (from rup in db.Ruptura
                                    join ap in db.Apresentacao on rup.Codigo_Apresentacao equals (ap.Codigo_Apresentacao)
                                    join mo in db.Motivo on rup.IDMotivo equals (mo.IDMotivo)
                                    join pdv in db.PDV on rup.CodigoPDV equals (pdv.CodigoPDV)

                                    where rup.IDMotivo != _idmotivo

                                    //group rup by new { rup.IDRuptura} into gr

                                    select new 
                                    {
                                        rup.IDRuptura,
                                        rup.DataRuptura,
                                        rup.IDMotivo,
                                        rup.Motivo.Motivo1,
                                        rup.IDOrigem,
                                        rup.CodigoPDV,
                                        rup.PDV.UF,
                                        pdv.Cidade,
                                        CnpjDescricao = pdv.Cnpj + " - " + pdv.Descricao,
                                        rup.Codigo_Apresentacao,
                                        ap.Unidade_Negocio,
                                        ap.Codigo_Unidade_Negocio,
                                        ap.Franquia,
                                        ap.Familia,
                                        ap.Descricao
                                    }).ToList().OrderBy(r => r.IDMotivo);

                foreach (var item in monta_arvore)
                {
                    //db.DeleteOnSubmit(item);
                }
            }
            catch (Exception ex)
            {
            }
        }

This is the error it gives:

'System.Data.Entity.DbSet<Ruptura.Models.Ruptura>' does not contain a definition for 'DeleteAllOnSubmit' and no extension method 'DeleteAllOnSubmit' accepting a first argument of type 'System.Data.Entity.DbSet<Ruptura.Models.Ruptura>' could be found (are you missing a using directive or an assembly reference?)