You didn't specify how much is charged per ride to determine revenue...but we can just use a variable p for the price charged per ride...
r(x)=px, c(x)=15x+200
To break even, P, profit must equal zero and P(x)=r(x)-c(x)
P(x)=px-15x-200
P(x)=0 when x(p-15)-200=0
x=200/(p-15)
So the number of rides needed, x, can be found once you determine what is charged per ride. :D *note from even this partial answer that p must be greater than 15 or you will never break even.
