Answer:
18 cars had air conditioning and automatic transmission but not power steering.
Step-by-step explanation:
To solve this problem, we must build the Venn's Diagram of these sets.
I am going to say that:
-The set A represents the cars that had air conditioning.
-The set B represents the cars that had automatic transmission.
-The set C represents the cars that had power steering.
-The value of d represents the cars that had none of those extras.
We have that:

In which a is the number of cars that only had air conditioning,
is the number of cars that have both air conditioning and automatic transmission,
is the number of cars that have both air conditioning and power steering. And
is the number of cars that had all those three extras.
By the same logic, we have:


How many cars had air conditioning and automatic transmission but not power steering?
This is
.
We start finding the values from the intersection of three sets
6 cars had all three of these extras. This means that

11 cars had both automatic transmission and power steering.
This is


25 cars had only power steering.
This means that 
62 cars had only automatic transmissions.
This means that
.
21 cars had only air conditioning
This means that 
80 had power steering
This means that 



Now, we can use the equation of A or B to find 
96 had automatic transmission. This means that 



18 cars had air conditioning and automatic transmission but not power steering.