I've gotten through the first few challenges without any real issue.  I'm stuck on this one, however.  In frustration I've used 'text.escapeSingleQuotes' combined with space replacement and whitelisting for the first 2 methods and then casting for the third since it's a Number.  I fail to see how this isn't enough to prevent SOQL injection, specifically because of the white listing.  I've tested against the whitelisting and it seems to be working correctly.  

I just wonder if this is a case of the challenge looking for a particular answer or I'm just missing something.

    public PageReference stringSearchOne(){
        string query = 'SELECT Id,Name,Quantity__c,Storage_Location__c,Storage_Location__r.Castle__c,Type__c FROM Supply__c';
        string whereClause = '';

        if(textOne != null && textOne!=''){
                whereClause += 'name like \'%'+string.escapeSingleQuotes(textOne.replaceAll('[^\\w]', ''))+'%\'';
                // textOne.replaceAll('[^\\w]', '')
        }
        Set<String> n = new Set<String>{'Barley','Beans','Bread','Cheese','Eels','Figs','Herrings','Horses','Malt','Oats','Raisins','Rice','Salt Beef','Salt Pork','Venison','Water','Wine'};
        if(whereClause != ''){
            if(n.contains(textOne)) {
                whereclause_records = database.query(query+' where '+whereClause+' Limit 10');        
            } else {
                whereclause_records = database.query(query+' where name = \'Venison\' Limit 10');
            }
        }

        return null;
    }


    public PageReference stringSearchTwo(){
        string query = 'SELECT Id,Name,Quantity__c,Storage_Location__c,Storage_Location__r.Castle__c,Type__c FROM Supply__c';
        string whereClause = '';

        if(textTwo != null && textTwo!=''){
                whereClause += 'Storage_Location__r.name like  \'%'+string.escapeSingleQuotes(textTwo.replaceAll('[^\\w]', ''))+'%\' ';
        }

        if(whereClause != ''){
            if(textTwo == 'Storeroom' || textTwo == 'Stables') {
                whereclause_records = database.query(query+' where '+whereClause+' Limit 10');
            }
        }

        return null;
    }


    public PageReference numberSearchOne(){
        string query = 'SELECT Id,Name,Quantity__c,Storage_Location__c,Storage_Location__r.Castle__c,Type__c FROM Supply__c';
        string whereClause = '';

        if(numberOne != null && comparator != null){
            whereClause += 'Quantity__c '+comparator+' '+string.valueOf(numberOne)+' ';
        }

        if(whereClause != ''){
            whereclause_records = database.query(query+' where '+whereClause+' Limit 10');
        }

        return null;
    }