This is not algebra, although you can solve it with algebra. It is a simple, 7th grade division problem. Everyone is trying to make it so difficult and are getting confused. It is the number 6 divided by the number 2(2+1). Now set it up as a division problem and solve.
6 6 6
----------- = ------------= ----= 1
2(2+1) 4+2 6
2(2+1) is one number and must be cleared before you divide into six. I believe that is where the confusion has arisen.