Step-by-step explanation: If there are 60 teachers and only 20% of the teachers donate, then you could say that there is only 0.2 of the teachers who donated boxes. This gives you 0.2 times 60 which equals 12. If each teacher donates 5 boxes each and there are 12 teachers who donated, then there would be a total of 60 boxes donated.
The answer is a, this is because 5(2+4) is the same as multiplying 5 by 6 to get 30. The reason we do this is because the length of the entire side is the sum of the bottom numbers