Devon is trying to find the unit price on a six pack of drinks on sale for $2.99 his sister said that a price each drink would cost just over $2 is she correct and how do you know if she is not how would devon sister find the correct price

If 6 drinks cost $2 each that would be $12 for the six pack and not $2.99

I would round the answer up to $3.00 and divide by 6 - You get $ .50  (50 cents) per drink.
If you use $2.99 instead of $3,00 you will get about $.498 cents which is really not practical since there are no coins you can use to buy a single drink.