The price of admission to the zoo is $8 per adult and $3 per child.
The total charge for a group is $97. 8 adult tickets were purchased.
How many child tickets were purchased?
Let's say the number of child tickets purchased is C.
The cost of the adult tickets is 8 * $8 = $<<8*8=64>>64.
The cost of the child tickets is C * $3 = $3C.
The total cost is $64 + $3C = $97.
Subtracting $64 from both sides of the equation, we get $3C = $97 - $64 = $33
Dividing both sides by $3, we get C = $33 / $3 = <<33/3=11>>11.
11 child tickets were purchased. Answer: \boxed{11}.