Let's break down the equation above. The original fraction is 2/9. The numerator represents the 6th grade students, and the denominator represents the total number of students in the school. So, if we expand that to actual numbers in the school, it would be 42 over the total number of students in the school (represented by x).
Using this method, each group of 60 players do not have the same chance of being selected.
Also with this method, the selection will not be uniformly distributed among the 30 teams. Some teams will have more players, some will have few and some will have no player selected at all.