5 cartoons have 30 x 5 = 150 boxes. And each box has 20 packets of biscuits. So there are 150 x 20 packets = 3000 packets. And each packet has 15 biscuits. Therefore total number of biscuits in 5 cartoons is 3000 x 15 = 45000 biscuits.
There are 2500 students. So each student will get 45000/2500=18 biscuits