Answer: Average annual salary of the 3 people is equal to Kate's annual salary.
Explanation:
Since we have given that
Difference between Mary's and Jim's annual salaries be m-j
Difference between Mary's and Kate's annual salaries be m-k
According to question, we get that

Average annual salary of the 3 people would be

Hence, average annual salary of the 3 people is equal to Kate's annual salary.