remove a few items (Id) from results

Hello ,

im trying to remove a few items from a query results using linqCore but its not removing them

code& results :

IQueryable<int> postOn = //Results=9(Id)OK 
                        _context.QuettaOffers.Where(d => d.SiteUserId == LoguserId).Select(s => s.QuettaReqId);

                    //Get all request that relevant to user without the one he already post on 
                    IOrderedEnumerable<QuettaReq> listOfR = //Results= 9,11 (Id) should be ..11(Id)
                        //IQueryable<QuettaReq> listOfR
                        _context.Quetta.Include(q => q.Category)
                            .Where(d => d.OfferDate > DateTime.Now && d.CatId == suplayerCat)
                            .ToList()
                            //.ToList()
                            .SkipWhile(a => a.Id.Equals(postOn))
                            .OrderBy(x => x.Id);
                    //  .TakeWhile(a => a.Id != postOn);

Thanks in advance