Betty deposits an amount now and withdraws another amount after 9 months. 2 years after the initial deposit her account balance is $7,096.529. Bob deposits twice what Betty did, now and withdraws after 15 months 300% of what she withdrew. 2 years after his initial deposit his account balance is $12,728.614.

If rates are 8% per annum effective then algebraically determine how much Betty deposited and withdrew.

(I need a step-by-step explanation of the formulas used. Thanks)