1/2 of the boxes means: 100/2 = 50
So, It took 2 1/2 hours to pack these 50 boxes. Let's write this in minutes:
1 hour = 60 min
2 1/2 hours = 2.5 hours = 2.5 * 60 min = 150 min
Thus, it took 150 min to pack 50 boxes. Now, to find the avarege time it took to pack each box, we divide 150 min by 50 boxes:
150/50 = 3
