War Lessons

This excerpt is written in a "this versus that" way, it shows a parallel. Paul is weighing the usefulness of the skills that he had learned in his previous life, to the skills he's learned from war. He's presenting the tasks in a way that almost devalues his previous skills, and deems his war skills more important and practical. These abilities are what have become important, they are what's valuable. There's a brief moment where Paul and his friends banter back and forth asking each other academic questions and it all seems entirely silly. That's because for them, school now seems irrelevant. It's a joke, something to life at, compared to the harsh realities of war. 
In school, students are taught subjects and are told "you will need this in the future". But Paul and his friends have no future, the war has taken that away from them. It does not matter to them wether or not they know mathematics or the meaning of cohesion. What actually matters to them is that they know how to survive, and how to get by. Things such as lighting a cigarette in a storm, and making fire with wet wood are day to day realities of life for these men during the war. Gritty situations that they just have to muddle through, it's a part of life now. Because of it's new importance, that's what would now qualify a man as "educated", because he knows how to get by. 
This quote really helps to show how much Paul and the other soldiers have changed. It shows what they no longer value and what they value now. What had seemed essential is now joke material. Tasks they hadn't even worried about before were now a part of every day life during the war. This quote shows the sad shift from up and coming young man, to hardened soldier.