Answer:
When adding up fractions you want to have the same denominator, and in 1/3, 2/3, 3/3 you do. Now you want to add up all the numerators and keep the denominator the same. 1+2+3=6.
Now you would have 6/3, and if you divide that out 6/3=2.
Your final answer would be 2.
Hope this helps ;)