From the problem, the total must not be more than $2 above or below $36
So the range must be from $34 up to $38 only
Let x be the cost of 1 angelfish, and the total cost for 6 angelfishes is 6x
The inequality will be :

Divide both sides by 6 :

The answer is $5.67 ≤ x ≤ $6.33