C++ :

#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>

using namespace std;

float RunningAvg(float);

int main()
{
	int x = 1;
	float avg;
	int n;

	cin>>n;

	while (x < 20)
	{
		avg = RunningAvg(x);
		cout<<"Average is: "<<avg<<endl;
		x= x +3;
	}
}

float RunningAvg(float a)
{
	static float total = 0.0;
	static int count = 0;
	total = total + a;
	count++;
	return total/float(count);
}