Answer:
A sixth grade silence club needs 180$ to pay for the tickets to a science museum.
1. Suppose there 15 students in the club, then each of them needs to pay
\dfrac{\$180}{15}=\$12 
15
$180
 =$12
This means each ticket costs $12.
2. Suppose each ticket cost $15, then there are
\dfrac{\$180}{\$15}=12 
$15
$180
 =12 students in the club.