Chemistry Lab

This is a short note of frustration.
On Thursday, my AP Chemistry class started an experiment to try and find the percent of copper in a sample of brass. It was one of the most confusing labs I had ever done, so that earlier today, when I finally decided to do my homework, I could not figure out how most of my data worked together. I read the background information over and over again, but I still did not understand how the absorption of the metal ion could help me figure out the percent of copper. It frustrates me to no end! Admittedly, I might not have been paying my fullest attention that day, but I know that the role of the absorption value was not mentioned. So late into the evening, even after asking my friend for some aid on post-lab questions, my lab is not completed. How am I supposed to write a conclusion about something I don't understand? And so, I am venting on this note, while I am fuming at my last pre-lab question. This lab has wasted hours for me, so I did not get to complete some of my to-dos. I am extremely vexed! During this week, I will be trying to finish the lab I could not over this weekend by the due date, which I believe is this Thursday. Hopefully I do not have a lot of homework tomorrow.