which is correct?

a couple billions of dollar

or

a couple billion of dollars

Neither --

"two billion dollars" would work just fine and is less iffy.

Commonly understood:
a couple = 2
a few = 3 to 5
several = 5 or more

And when you use "a couple" in a sentence like this, you need to add the word "of" after it: e.g., I have a couple of CDs I'd like to get rid of.

then would "it cost them billions of dollars" work?

i just don't know is the -s on billion or dollar.

Yes, you could say any of these:

It cost them billions of dollars. (Make sure it's clear what "it" is.)

It cost them two billion dollars.

It cost them a couple of billion dollars. (This is not as formal as the other two, however.)

What is your choice?

=)

The correct expression is "a couple of billion dollars."

To understand why, let's break it down:

1. "A couple of" means two or a small number of something. It implies an approximate quantity.

2. "Billion" refers to the number 1,000,000,000 (one billion), which is an extremely large number.

So when we say "a couple of billion dollars," it means approximately two billion dollars.

Now, let's address the incorrect options you mentioned:

- "A couple billions of dollar" is not grammatically correct. There should be an "of" after "couple" to indicate the quantity, but "billions" should not be pluralized.

- "A couple billion of dollars" is also not correct. "Billion" should not be pluralized, and "of" should come before "billion" to indicate the quantity.

Therefore, the correct expression is "a couple of billion dollars."