Ray counted a total of 40 white cars and yellow cars. There are 9 times more white cars then yellow cars. How many white cars did Ray count.

if there are x yellow cars, there are 9x white cars

so, add them up:

x + 9x = 40
10x = 40
x = 4

Now you know how many yellow cars there are, so you can figure out how many white ones there are.