Average speeds of each car are 43 mph and 40 mph.
Solution:
Given that
Distance between two cars are 166 miles.
Cars are travelling towards each other on same road.
Two cars meet in 2 hours.
One car travels 3mph faster than the other.
Need to calculate average speed of each car.
Let assume faster car be A and slower car be B
Let say Speed of car B be represented by x mph
As car A is faster having speed 3mph faster than slower one that is B
So Speed of car A be represented by x + 3 mph
Distance traveled by car A in 2 hrs = speed x time = (x + 3 )2 = 2x + 6

As both car meets after two hrs, so combined distance travelled by both cars = 166 miles
2x + 6 + 2x = 166
=> 4x = 160
=> x = 40
Speed of Car A = x + 3 = 40 + 3 = 43 mph
Speed of Car B = x = 40 mph
Hence average speeds of each car are 43 mph and 40 mph.