Can somebody help me out with this geometry homework? It's too complicated.

For what value of x does 4x = (1/8) x + 5?

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)