15 boxes - 3 boxes = 12 boxes
12 boxes x 8 pens/box = 96 pens
The simpler problem is:
Now, let's apply this insight to the more complex problem. If Tom has 15 boxes of pens and gives 3 boxes to his friend, we can calculate the number of pens he has left as follows: My Homework Lesson 8 Problem Solving Work A Simpler
"Tom has 1 box of pens. Each box contains 8 pens. If he gives 0 boxes to his friend, how many pens does Tom have left?" 15 boxes - 3 boxes = 12 boxes
Therefore, Tom has 96 pens left.