Answer:
$8.85
Step-by-step explanation:
This a question of direct variation, so we can make out a relationship between the two factors. 12 is 2/3 of 18, so the cost of 12 would also be 2/3 of the cost of 18. We can now make an equation to solve.

The answer is 29 classmates.
-Blue has 7 people
-Brown has 15 people
-Green has 4 people
-Hazel has 3 people
When all added up 29 classmates.
Are you sure this question is right? there are no negatives? i’m pretty sure the answer is 72 but if i’m wrong, i’m sorry.