So, we have two options: option 1: a can of tomatoes for 53 cents. option 2: a can of tomatoes for 70 cents with a 20% discount.
First we have to determine the price of the 2nd option. 10 % of 70 cents is 7 cents 20 % of 70 cents is 14 cents. So, we have 14 cents of discount, which makes the new price (70-14=) 56 cents.
Now our two options are either 53 or 56 cents. Therefore option 1 is the best buy available.