At the zoo, a cage had 93 snakes and 97 alligators. If 40 alligators were hiding how many alligators were not hiding?
There are $93$ snakes and $97$ alligators in the cage. 

$x$ - the number of alligators hiding. 

$y$ - the number of alligators not hiding. 

Then we have the equation: 

$93 + 97 = 40 + y$

$y = 97 - 40 = 57$

So, $57$ alligators were not hiding.