I need help with these two questions and for number 15 it's just two of them not three.​

If the value of cos330°is√3/2 then find cos 165°.

Factor the polynomial expression x6 – x3 – 20

Graham’s monthly bank statement showed the following deposits and withdrawals. -$25.20, $42.75, -$22.04, -$18.50, $74.11. part a if grahams baldness in the account was $37.86 at the beginning of the month,! 27/4! 2// the account balance at the end of the month? ? plz i will give you 100 points