Final answer:
To calculate the percentage increase in Jill's salary, divide the difference between her current and previous salaries by her previous salary and multiply by 100. The percentage increase is 20%.
Step-by-step explanation:
To calculate the percentage increase in Jill's salary, we first need to find the difference between her current salary of $84,000 and her previous salary of $70,000. The difference is $14,000. To find the percentage increase, divide the difference by her previous salary and multiply by 100. So, the percentage increase is (14,000/70,000) x 100 = 20%.