So there are four teachers and they want 3 boxes. If you are trying to find out how many pencils they get. You multiply it by 96. Since there are 96 pencils and a box and 96 come in a box.
96x3=288
If they want to share it they each get 72. Since there are 4 teachers and 288 pencils you divide 288 by 4.
288/4=72.