The two cars have been driving for three hours, and the ratio of the distance traveled to the distance not traveled is 2: 3. In other words, the two cars walked for three hours, only 40%(2/5) of the whole journey, leaving 60% of the distance. The time spent can be directly calculated as follows:

3/(2/3)= 3*(3/2) = 9/2 =4.5 (hours)

It will take 4.5 hours for the two cars to meet.