Okay so I stumbled upon this question and I think I may be on the right track but request backup..

A store handles a specialty item that has a marginal cost of $24 and a fixed cost of $360. The sales required to break even are 75 items.

A) Find the linear cost function

*My answer was --> c(x) = 24***x**+360 did you forget the **x** ?
B) Find the linear revenue function

*My answer was --> R(x) = px -->R(x) = 384x* R(x) = C(x) at the break even point

p = selling price

75p = 24(75) + 360

p = 28.80

R(x) = px = 28.80x