The equation that could be used to find how many charms are on a bracelet that costs $96 will be: 
 and they can buy 14 charms.
Step-by-step explanation
The cost of a charm bracelet is $12 without the charms and the additional cost is $6 for each charm. 
If the number of charms added to the bracelet is '
' , then the total additional cost for the charms will be: 

Given that, the total cost of the bracelet with charms is $96. 
So the equation will be: 

Now solving the above equation, we will get.....

Thus, they can buy 14 charms.