Are you intentionally dense? Let me break it down for you:
Within a theoretical communist community, you have three farmers
Farmers A and B are inexperienced; Farmer A produces 2 measures of wheat, and Farmer B only produces 1
Farmer C is much more skilled at farming, and produces 6 measures of wheat
Under the principles of communism, half of Farmer C's yield is taken and given to the other two, so all three farmers end up with 3 measures of wheat
Do I have to show you the math? (1 + 2 + 6) / 3 = 3