Dear Mrs Teacher
Hope you are fine.
I am writing to say sorry because I did not send my assignment on time.
I was sick in the last few days, so I could not finish it. I know it is important to send work on time, and I am very sorry for the problem.
I have finished the assignment now, and I can send it to you today if it is OK. If you want, I can also do some extra work to fix my mistake.
Thank you for your understanding. I will try to be better with deadlines next time.
Best regards,
Tomáš Foltýn
