They can form 6 groups, each having 2 coaches and 7 players.
Here you want to find the GCF, or Greatest Common Factor for 12 and 42.
The easiest way to do it would be to list out all the factors, and when you do so, you'll see that the greatest number that matches is 6.
So now you know there are 6 groups. Now just divide the coaches and players by six groups.
12/6 = 2 coaches
42/6 = 7 players