The ratio of the number of pencils that Isaac has to the number of pencils that Pablo has is 2:7. Together they have 72 pencils. How many pencils does Isaac have?

If you divide 72 by 9 (both sides of the ratio added together) you get 8. if you multiply 8 to both sides of the ratio 2:7 you get 16:56. if you add 16 and 56 together, you will receive 72. Therefore, Isaac has 16 pencils