RatiosUnit rate
Find the unit rate for each.
A unit rate is the price of one, the distance in one hour, the amount in one packet. These free printable worksheets give the total and the count and ask for the per-one figure — the form comparisons are actually made in.
If they get stuck

The answer key prints on a separate page.
$10 for 2 is $5 each, and once both offers are written that way the better one is obvious. That is the whole reason the skill exists: two ratios in their original form are hard to compare, and two unit rates are a glance apart. Supermarket shelf labels do this in small print for exactly this reason.
The arithmetic is a division and the difficulty is knowing which way around. Total divided by count, always — dollars divided by items gives dollars per item, and the unit of the answer says whether it was done the right way. Reading the answer's units aloud is the check worth building in.
$10 for 2 = $5 each