number.h

template<typename type>
class number
{
private:
	type	value_;

public:
	number(void) : value_(0)
	{

	}

	number(const type value) : value_(value)
	{

	}

	~number(void)
	{

	}

	type	getValue(void) const;
	void	setValue(type value);

	type	operator +(number other);
	type	operator -(number other);
	type	operator *(number other);
	type	operator /(number other);
};

number.cpp

//*********************************************************************//
#include "number.h"

//*********************************************************************//
template<typename type>
type number<type>::getValue(void) const
{
	return(value_);
}

//*********************************************************************//
template<typename type>
void number<type>::setValue(type value)
{
	value_ = value;
}

//*********************************************************************//
template<typename type>
type number<type>::operator +(number other)
{
	return(value_ + other.getValue());
}

//*********************************************************************//
template<typename type>
type number<type>::operator -(number other)
{
	return(value_ - other.getValue());
}

//*********************************************************************//
template<typename type>
type number<type>::operator *(number other)
{
	return(value_ * other.getValue());
}

//*********************************************************************//
template<typename type>
type number<type>::operator /(number other)
{
	if(other.getValue() == 0)
		return 0;

	return(value_ / other.getValue());
}

und main.cpp

#include <iostream>
#include "number.h"

using namespace std;

int main()
{
	number<int> zahl1(20);
	number<int> zahl2(13);

	cout << "operator+ (20, 13) == " << zahl1 + zahl2 << endl;

	return 0;
}

folgender fehler:
error LNK2019: Verweis auf nicht aufgelöstes externes Symbol ""public: int __thiscall number<int>::operator+(class number<int>)" (??H?$number@H@@QAEHV0@@Z)" in Funktion "_main".

// number.h

template<typename type>
class number
{
//...
};

#include "number.cpp"

Genausogut kannst du die Implementierung direkt in den Header aufnehmen.