Please see image below- 8th grade math

What is the greatest common factor of 6a, 8a^{2}, and 14?

A) if $50000 is invested in a bank account that pays 9.3% of interest compounded on a six-monthly basis, how much money will be in the account after 3 and 12 years? b) if matusalen's father had put $2.0 in the bank when he was born and there, how long would matusalen have had to his death (969 years later) if the interest was 7% per year composed each month and weekly?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?