Hey there!
To find the answer to this problem, all you need to do is find the greatest common factor between these two numbers. In this case, it's 21. You can multiply 21 by two different numbers to get 105 and 147. When you divide 105 by 21, you get 5 pens. When you do the same with 147, you get 7.
The greatest number of sets you could make is 21. Each set will come with 5 pens and 7 pencils.
Hope this helped you out! :-)
