Final answer:
There are 132 ways to enter the building by one door and leave the building by a different door.
Step-by-step explanation:
In order to enter the building and leave the building by different doors, we need to consider that there are 12 options for entering and 11 options for leaving (since we can't use the same door twice).
To find the total number of ways, we multiply the number of options for entering (12) by the number of options for leaving (11). So the total number of ways to enter and leave by different doors is 12 x 11 = 132.