Final answer:
To find the number of people who had a parakeet only, subtract the number of people who had both a dog and a cat from the total number of people who had a dog or a cat. The answer is 75 people.
Step-by-step explanation:
To find the number of people who had a parakeet only, we need to subtract the number of people who had both a dog and a cat from the total number of people who had a dog or a cat.
From the given information, we know that 51 people had a dog, 40 people had a cat, and 16 people had both a dog and a cat.
To calculate the number of people who had a dog or a cat, we add the number of people with a dog and the number of people with a cat: 51 + 40 = 91.
Now, we can subtract the number of people who had both a dog and a cat from the total: 91 - 16 = 75.
Therefore, 75 people had a parakeet only.