Break a part the addends to find the sum 18+21

Answer question above and explain each step : )

Aschool puts on a play. the play costs $1,200 in expenses. the students charge $4.00 for tickets. there will be one performance of the play in an auditorium that seats 500 people. what is the domain of the function that shows the profit as a function of the number of tickets sold?  

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