Let r = the rate of the slower car.
>>the rate of the faster car exceeded the rate of the slower
car by 6 kilometers per hour.<<
So r+6 = the rate of the faster car
>>traveling toward each other<<
So their approach rate is the sum of their rates = r+r+6 = 2r+6
From 11AM to 2:30PM is 3.5 hours.
>>from towns 315 kilometers apart<<
So their original distance apart went from 315 km to 0 km distance
apart in 3.5 hours, so
using Distance = Rate∙Time, with Distance = 315 km,
Approach Rate = 2r+6, and Time = 3.5 hours
315 = (2r+6)(3.5)
Solve that and get r = 42 km/hr for the slower car, and
r+6 = 42+6 = 48 km/hr for the faster car.
Edwin