360 miles in 4 hours is 90 miles per hour. But the thing is the car is driving slow, making it 15 miles per hour.
That's when you have to subtract 90-15 and that gives you the answer of 75. But we're not done just yet, you have to divide both of the equations below by 75.
360 / x = 75
360 = 75x
And it will give you a total of 4.8, therefore 4.8 hours is how long the car will take to travel the same distance.