X(9+3x) if x=5 what is the answer

Acar dealership pays you 5% commission on your first $10,000 on car sales and 8% commission on the sale amount over $10,000 if you sold a $12,000 car how much is your commission

Idont understand math at all! : o( use this scenario to answer the remaining questions: brenton purchased a new bedroom set for $4,500.00. he lives in arizona and pays a 8.75% sales tax. if he made a 50% down payment and financed the rest, what amount did he finance? what is the total sales tax brenton will pay? enter your answer in currency format, round to the nearest cent. what was brenton's total amount financed? enter your answer in currency format, round to the nearest cent.

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)