I've uploaded a photo with the answer because it's too hard to do this out on the computer.
Answer:
2304 pens
Step-by-step explanation:
well 16 box with 144 pens in each just multiply to get 2304 pens that he stacked
Peter paid 0.85 tax which is at 7.1% sales tax
Answer: the area for the square is 126.56cm²: