I personally understand it like this:
You have (7*4)*(3*5)*(3*2)*1 combinations. (If you do not understand there are some really good posts that are explaining it really well, espacially the one of Brunel)
BUT the questions says that we need to find the number of different
For the first one, the total of the possibilities is 7*4. That means that you have 7 possibilities, and that the team can be spread in 4 groups! But here, we are only looking for the number of different teams. Therefore, if groupe AB can be spread in team 1, 2, 3 or 4 = the number of different combinations is 4 but we still have ONE same team.
In consequence, what do we have to do? Divide by 4 for (7*4), 3 for (3*5), 2 for (2*3) or in other term divide the whole by 4!
Hope it helps.
Think outside the box