On Friday, 120 cars were in the parking lot. What percent of the total number of cars were in the parking lot on Friday?

Since the total number of cars is 200 on Friday there were (in percent)

(the number of cars on Friday / the total number of cars) * 100

(120/200)*100 % = (12/20) *100 % =(3/5) *100 % = 60 %

On Friday there were 60% of cars.

The number of cars on Saturday = total number of cars - number of cars on Friday

The number of cars on Saturday = 200 - 120 = 80 cars

Similar as for Friday for Sathurday the percentage will be (80/200)* 100 = 40%

On Saturday there were 40% of cars.

Or by knowing that on Friday there were 60% and the rest were on Saturday we conclude that on Saturday there were 100 - 60 = 40% of the cars.