3x+12-6x< -9how do i do this?

If anyone has done the algebra 2 chaos theory portfolio would you be wiling to me? i kind of know what i'm doing i just don't know if i'm doing it right.

Evaluate-27 ^4/3/8 a) - 81/16 b) 81/16 c) 16/81

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?