The pens cost $10 if the total was $37
Work:
Pen: ||||||||||
Pencil: |||||||||
Pencil: |||||||||
Pencil: |||||||||
Basically the division groups you probably learned in elementary.
Because the question mentioned that pens were $1 more than pencils. Pens automatically start with one extra in sorting.
9(3) + 10
= 37
(9+9+9) + 10
= 37
Above adding everything together to get our answer.