If you’re asking for the cost of the drink, the drink would be $1. This is because 2 sandwiches would cost $10 and that means 1 sandwich would make it $5. If 2 sandwiches cost $10, the remaining $2 in the $12 dollars would be the drinks. 2 drinks for $2 would make 1 drink for $1. So the cost of 5 drinks is $5 or $1 per drink.
If confused, don’t be shy to ask :)