I suspect the part that's giving you trouble is figuring out how the bus drivers wage depends on x. Use the formula distance=rate x time.

NY to Boston is 225 miles, rate is x. So time = (225 miles)/x(miles/hour) = 225/x hours.

The bus driver's total wage from the trip is

12.50(dollars)(time)/hour = 12.50(dollars)(225/x)(hours)/hour = 12.50*225/x dollars.

Make sure your final equation has the right units of currency (right now there are both dollars and cents).