Since car A travels 50 miles in one hour
Since the rule of the speed is speed = distance/time, then
The speed of car A = 50/1 = 50 miles per hour
Since car B travels 160 miles in two hours, then
The speed of car B = 160/2 = 80 miles per hour
To find the average speed of them sum them up and divide the sum by 2
The average speed of car A and car B = (50 + 80)/2 = 130/2 = 65 miles per hour
The average speed of both cars is 65 miles per hour