Determining the tone of a literary work requires you to think about what the author's attitude or opinion is of the topic. The best way to analyze tone is to review the chapters mentioned and look closely at the word choice and language of the author. Authors make deliberate and subconscious choices that reveal their tone to the reader. Focus on the connotative meaning of the words that they are using and whether these language choices result in a positive or negative tone.
Another craft technique to consider is the imagery the author is creating in these chapters. The imagery used can convey a tone very clearly to the reader.
In order to think about the author's tone in A Long Way Gone, you will want to focus on what the author believes about the situations that are occurring in the text. The tone in a story can be joyful, serious, humorous, sad, threatening, formal, informal, pessimistic, and optimistic. Remember that a text can have many different tones, so really hone in on the chapters that you are being asked about.