Cars Math Puzzle – How many cars in the parking ?

lets say there are total x cars, thus
x/10 number of cars are yellow initially.

as yellow car’s percent increases from 1/10th to 1/9th after new car arrives, so new car must be a yellow car.
So we can form this equation

1 + x/10 = (x+1)/9

Now we just need to solve this equation
on multiplying both sides by 9*10 =>
9*10 + 9x = 10x + 10
90 – 10 = 10x – 9x
x = 80

So there were 8 yellow cars initially among a total of 80 cars(i.e. 1/10th)
and a new yellow cars comes making 9 yellow cars in total of 81 cars.(i.e. 1/9th)

So answer to the question is 81. there are a total of 81 cars now.