Errors for the Queue.h file are: Queue.h:52: error: expected unqualified-id before 'using' Queue.h:52: error: expected initializer before 'using' I've never used the 'using' keyword before, so I'm pretty sure I must have messed that up somehow. Errors in LinkedList.h are redefinition of classes errors.

LinkedList.h

using namespace std; 
#include <iostream>
#ifndef LINKEDLIST_H
#define LINKEDLIST_H

template <class T>
struct Node 
{
    T val; 
    Node<T> *next; 
};

template <class T>
class LinkedList
{
    public:
        LinkedList();
        ~LinkedList();
        void insertAtBack(T valueToInsert);
        bool removeFromBack();
        void print();
        bool isEmpty();
        int size();
        void clear();

        void insertAtFront(T valueToInsert);
        bool removeFromFront();

  T& firstNum();

 
    private:
        Node<T> *first; 
        Node<T> *last; 
};

#endif

/*****************LINKEDLIST CPP FILE******************/

template <class T>
LinkedList<T>::LinkedList()
{
	first = NULL;
	last = NULL;
}

template <class T>
LinkedList<T>::~LinkedList()
{
	Node<T>* temp = first;
	while(temp != NULL)
	{
		temp = temp->next;
		delete(first); 
		first = temp;
	}
}

template <class T>
void LinkedList<T>::insertAtBack(T valueToInsert)
{
	Node<T>* newNode;
	newNode->val = valueToInsert;
	newNode->next = NULL;

	Node<T>* temp = first;

	if (temp != NULL) 
	{
		while (temp->next != NULL) 
		{
			temp = temp->next;
		}

		temp->next = newNode;
	}
	else 
	{
		first = newNode;
	}
}

template <class T>
bool LinkedList<T>::removeFromBack()
{	
	if (first == NULL && last == NULL) {return false;}

	if (first == last)
	{
		cout<<"First is equal to Last."<<endl;
		delete(first);
		first = last = NULL;
		return true;
	}

	else
	{
		Node<T>* temp = first;
		int nodeCount = 0;

		while (temp != NULL)
		{
			nodeCount = nodeCount + 1;
			temp = temp->next;
		}

		Node<T>* temp2 = first;
	
		for(int i = 1; i < (nodeCount - 1); i++)
		{
			temp2 = temp2->next;
		}

		cout << temp2->val<<endl;
		delete(temp2->next);
		
		last = temp2;
		last->next = NULL;
		
		return true;
	}
}

template <class T>
void LinkedList<T>::print()
{
	Node<T>* temp = first;

	if (temp == NULL) 
	{
		cout<<"";
	}

	if (temp->next == NULL) 
	{
		cout<<temp->val;
	}
	else 
	{
		while (temp != NULL)
		{
			cout<< temp->val;
			temp = temp->next;
			cout<< ",";
		}
	}
}

template <class T>
bool LinkedList<T>::isEmpty()
{
	if (first == NULL && last == NULL) {return true;}
	else {return false;}
}

template <class T>
int LinkedList<T>::size()
{	
	if (first == NULL && last == NULL) {return 0;}

	Node<T>* temp = first;
	int nodeCounter = 0;

	while (temp != NULL)
	{
		nodeCounter = nodeCounter + 1;
		temp = temp->next;
	}
	return nodeCounter;
}

template <class T>
void LinkedList<T>::clear()
{
	Node<T>* temp = first;
	while(temp != NULL)
	{
		temp = temp->next;
		first = temp;
		delete(temp);
	}
}

template <class T>
void LinkedList<T>::insertAtFront(T valueToInsert)
{
	Node<T>* newNode;

	newNode->val = valueToInsert;

  	 if(first == NULL)
   	{
   		first = newNode;
   	}
   	else
   	{
   		newNode->next = first;
   		first = newNode;
   	}

}

template <class T>
bool LinkedList<T>::removeFromFront()
{
	if (first == NULL && last == NULL) {return false;}
	
	else
	{
		Node<T>* temp;

		temp = first;
		first = first->next;

		delete(temp);

		return true;
	}
}

template <class T>
T& LinkedList<T>::firstNum()
{
	return first->val;
}

Queue.h

using namespace std;
#include <iostream>
#include "LinkedList.h"
#ifndef QUEUE_H
#define QUEUE_H

template <class T>
class Queue: public LinkedList<T>
{
  public:
		Queue();
		~Queue();
		
		void enqueue(T value);
		T dequeue();
		T& front();		
};

#endif

/****************QUEUE CPP FILE****************/

template <class T>
Queue<T>::Queue(){}

template <class T>		
Queue<T>::~Queue(){}

template <class T>		
void Queue<T>::enqueue(T value)
{
	insertAtBack(value);
}

template <class T>	
T using LinkedList<T>::dequeue()
{
	if(isEmpty())
	{
		throw 2;
	}
	else
	{
		T firstElmnt = firstNum();
		removeFromFront();

		return firstElmnt;
	}
}

template <class T>	
T& using LinkedList<T>::front()
{
	if(isEmpty())
	{
		throw 3;
	}
	else
	{
		return firstNum();
	}
}