Let "r" be the rate of the slower car, in mph.

Then the speed of the faster car is (r+7) mph.

In 4 hours, the slower car covered the distance of 4*r miles, while the faster car covered the distance of 4*(r+7) miles.

The sum of these distances is 492 miles, which gives you ann equation

4r + 4*(r+7) = 492.

4r + 4r + 28 = 492,

8r = 492 - 28  --->  8r = 464  --->  r =  = 58.


Answer. The slower car speed was 58 mph.  The faster car speed was 58+7 = 65 mph.