To determine how many people in the sample have three or more pets in their household, we need to add the responses that indicate three or more pets.
From the given responses, we have:
- 18 (people with pets)
- 6 (people with pets)
- 7 (people with pets)
- 3 (people with pets)
Assuming that "18," "6," "7," and "3" each represent the number of people with increasing counts of pets (e.g., one group having 3 or more pets), it seems likely that the response with "18" is the total number of people with three or more pets.
Thus, the total number of people in this sample who have three or more pets in their household is 18.