HELP! Urgent! What is the answer.

Sole the equation 6n + 9 = -3n - 21 - 6 for n

Darcy deposited $390 into a savings account. as long as the account balance remains at or above $150, she does not have to pay a service fee for the account. for how many months can she withdraw $40 a month without having to pay service fees? a) 3 b) 5 c) 6 d) 9

Explain how to convert measurements in the metric system