What does a a isolate variable mean?

Which of these people has balanced their checkbook correctly? oa. gary: the balance in his check register is $500 and the balance in his bank statement is $500. b. gail: the balance in her check register is $400 and the balance in her bank statement is $500. c. gavin: the balance in his check register is $500 and the balance in his bank statement is $510.

Just tell me how to set up the equation.

If the scale factor between two circles is 2x/5y what is the ratio of their areas?