Translation:Every day I go to work before they have breakfast.
đều (both) supports mỗi ngày (everyday) to indicate repetition on the action that happens everyday. If "đều" wasn't present here, the sentence would still be understandable but not as commonly used.
So let's say that mỗi ngày - đều sticks together. Example: mỗi ngày tôi đều học trên Duolingo (Everyday I study on Duolingo).
đều means both: Chúng tôi đều là học sinh = We are both students. It's just the way we speak. I am sure you'll be familiarized if you pursue Vietnamese longer. But for now let's not complicate things :)
At the beginning, I was like you, wondering why there are some words that appear to be optional, now I understand why they are here, not to make confusion, but it s just more natural to add. Like chinese, some words are in the sentences because that's why the way the Chinese say ;-)
So I translated this as "Every day I go to work before them to eat breakfast." It was marked wrong. How would the sentence above be translated differently from what was given?
I am not completely sure, but your translation would be correctly written as: " Mỗi ngày tôi đều đi làm trước khi họ để ăn sáng." Để means "in order to".