Mary is traveling cross country on a road trip. so far, mary has traveled 200 miles in her car and 200 miles by train. the car traveled at a rate that was 30 miles per hour slower than the train. mary modeled the total time for her trip with the following expression. what does x - 30 represent in this situation? the speed of the car the speed of the train the total distance traveled by the train the total distance traveled by the car