To determine how many invitations each person has to take to the post office, divide the total number of invitations by the number of people mailing them.
There are 225 invitations and a total of 5 people (Susan, Benjamin, and the three members of the bridal party).
So, the calculation is:
225 invitations รท 5 people = 45 invitations per person.
The correct response is: 45.