This problem calls for calculating the unit cost in each case and then comparing the unit costs.
$1.79
---------- = $0.09/oz
20 oz
Noting that 1 lb = 16 oz,
$2.59
---------- = $0.14
18 oz
$1.79 for 20 oz is definitely the better buy (less expensive) when compared to $2.59 for 18 oz.
