Let W = number of white cars, and Y = number of yellow cars.
There were 9 times as many white cars as yellow cars. This means that the number of white cars was 9 times more than the number of yellow cars. This can be translated by the expression:
9Y = W
The person counted 40 cars in total:
W + Y = 40
So we get the system:

In the first equation, we multiply by 9:
9W + 9Y = 360
In the second equation:
9Y= W
W-9Y = 0
Then we add the first with the second equation:
9W + 9Y + W - 9Y = 360
10 W = 360
W = 36
So He counted 36 white cars.
Hope this Helps! :)
Answer:

Step-by-step explanation:
Using the Foil method
you multiply x times x and get
Then you multiply -4 times X and get -4x
Then you multiply -3 times X and get -3x
then you add -4 and -3 together and get -7x
Lastly you multiply -4 and -3 and get 12
And there you have it

For this case the first thing you should know is the following unit conversion:
1 yard = 3 feet
Applying the conversion we have:
6 * (1/3) = 2 yards
Therefore the number of skeins of yarn is:
N = (36) / (2)
N = 18
Answer:
You need 18 skeins of yarn
Answer:
A
Step-by-step explanation:
p^-8q^-20 * p^8q^-10
=q^-30
=1/q^30