Based on the data,
- Starting with the resorts that have a spa, which are 30,
- We subtract those resorts that include both a spa and a children's club, which are 11, to exclude the ones with the latter feature.
- We now have (30 - 11) = 19 which are either only spa resorts or shared with a fitness center.
- However, we also need to exclude those that include both a spa and a fitness center which are 16.
- Now, we have (19 - 16) = 3.
- But, there are resorts that include all three features, which are 9. Since these have been subtracted twice in the previous steps, we now need to add them back.
- Therefore, the resorts that only have a spa are (3+9) = 12.
So, there are that have only a spa, according to the survey.
Answer: 12 resorts