How do i find population standard deviation

Dakota earned $7.50 in interest in account a and $18.75 in interest in account b after 15 months. if the simple interest rate is 4% for account a and 5% for account b, which account has the greater principal? explain. to make it a little easier, there is an image. good luck!

East black horse $0.25 total budget is $555 it'll cost $115 for other supplies about how many flyers do you think we can buy

Joanie watched 1 out of three of a movie in the morning