Define a variable for the number of cars, and define a variable for the number of vans or trucks. You will need to choose x for one and y for the other.

See below!

Step-by-step explanation:

I don't think you included the entire question, but maybe you were just stuck on this part, so I'm happy to help!

You include variables in a math equation to give meaning to a word, phrase, or situation in a shortened way.

For example, if I say, "I run 2 miles every day. How many miles will I run in x days?", your equation should look like this:

miles=2x

Notice that the 2 is a number, because that is the one thing that we know for sure. We know, no matter what, I run 2 miles a day. However, we don't know for how many days. So, for this, we need to put something as a sort of placeholder until we are told how many days.

Variables can be any letter, from A-Z! It is reccomended to stay with letters that avoid s, and i(among others) to make sure that you are using letters that can't be mistaken as letter on accident. For example, s could look like 5. In some cases, i could look like 1.

For your question, you could use:

#of cars=x

#of trucks/vans=y