The time taken by Jill and Cheryl to double their money is 12 years and 18 years respectively.
<h3>What is Algebra?</h3>
Algebra is the study of mathematical symbols and the rule involves manipulating these mathematical symbols.
Jill invested $500 in an account with a compound interest rate of 6%.
Cheryl invests $600 in an account with a compound interest rate of 4%.
The number of years each doubles their money. Using the relation of 72.

where r is the interest rate and t be the time
The time for the Jill will be

The time for the Cheryl will be

More about the Algebra link is given below.
brainly.com/question/953809