Which one is a better buy a 10 ounce bag for 1.99 or a18 ounce bag per 299?

Make the bag size totals the same, then see price total:

180 ounce total = 10 ounce x 18 = 1.99 x 18 = 35.82

180 ounce total = 18 ounce x 10 = 2.99 x 10 = 29.90

so 18 ounce is cheaper.