Final answer:
The comma in the sentence should be placed after 'Coke' to separate the items in the list, which are 'two hamburgers', 'a Coke', and 'a large order of fries'.
Step-by-step explanation:
The comma in the sentence 'Amy ordered two hamburgers, a Coke, and a large order of fries' belongs after 'Coke'. This is because we use commas to separate three or more elements in a series.
Adding a comma before the last item, also known as the Oxford comma, is considered by many as a general academic convention although it is not mandatory.
Consistency throughout your writing is key, so if you choose to use the Oxford comma, make sure to use it in all series.
In the given sentence, the list of items Amy ordered is made up of 'two hamburgers', 'a Coke', and 'a large order of fries'.
Therefore, the commas are correctly placed after 'hamburgers' and 'Coke' to separate these elements in a series.