Which is a better price: 5 for $1, 4 for 85¢, 2 for 25¢, or 6 for $1.10

Short answer 2 items for 25 cents.
To solve this, all you have to do is divide money by the number of items.



You put it into your calculator in exactly the same order.
Money
÷
Number of items
= 

So in this particular question
1 dollars  / 5 items = 0.20 dollars / item

0.85 dollars / 4 items = 0.2125 cents 

0.25 dollars / 2 items = 0.125

1.10 dollars / 6 items = 0.18333

Which gives you the best value for your money?
.25 spent on 20 items. The order is determined by the larger the amount on the right of the equal sign, the more expensive the item.