Answer:
24 and 48
Explanation:
Let's let the two numbers be a and b. 
Their sum is 72. So: 

One number (let's use a) is two times another (b). In other words: 

We have a system of equations. We can solve by substituting the second equation into the first. So: 

Combine like terms: 

Divide both sides by 3: 

So, one of the numbers is 24. 
Since their sum is 72, this means that the other number is 72-24 or 48. 
So, our two numbers is 24 and 48. 
And we're done!