At the zoo, a cage had 93 snakes and 97 alligators. If 40 alligators were hiding how many alligators were not hiding?
Let's denote the number of alligators by a, the number of snakes by s, and the number of alligators that were hiding by h. 

Then we have the following system of two equations with two unknowns: 

a+s=93 
a-h=57 

We can solve this system using different methods. For example, we can use substitution: 

a+s=93 
a=57+h 

a+s=93 
57+h+s=93 

57+s=93 
s=36 

a=57+h 
a=57+40=97 

Therefore the answer (numeric) is: 

97-40=57