Answer
The 18 oz jar is the better buy.
Work Step by Step
A unit price has 1 in the denominator.
$\frac{\$1.49}{18oz}=\frac{\$1.49\div18}{18oz\div18}=\frac{\$0.083}{1oz}$
$\frac{\$2.39}{28oz}=\frac{\$2.39\div28}{28oz\div28}=\frac{\$0.085}{1oz}$
$.083
