Answer: 20 ounces box of cheerios is cheaper.
Explanation:
If 10 ounce box of cheerios cost $2.80 and 20 ounce cost $5.20 then to find which is cheaper, you need to find the unit price which is the cost of an ounce.
Divide the money by the amount of ounces.
2.80 / 10 = 0.28 which is 28 cents per ounce.
5.20/20 = 0.26 which is 26 cents per ounce.
So the 20 box of cheerios is cheaper because it is 2 cents less.