Формальное:
Dear Sir or Madam,
I am writing to enquire about language courses organised by your school. I found out information about it in local newspaper and I would like to know more.
Even if Icannot certify my knowledge of English, after years of learning the language at school I can safely assume that I am an upper-intermediate student. Are you able to offer me any course that would be good for me?
I understand from your advertisment that your courses are free. Are they free for everyone, or just only for students from your school?
Неформальное:
Dear Tom,
It’s good to hear from you again. I hope you’re well and everything’s alright. I’m sorry that I didn’t reply to your letter earlier, but I was a little busy. I was on a holiday trip and I want to tell you about it. I’ve got so much to tell you.
I was on a trip to Paris. I was two weeks in that city and I must say it’s amazing. The Eiffel Tower and the Louvre Galleries were so cool, even if they were too overcrowded. Same with the most awaited Musee d’Orsay, with it’s Impressionist collection it was impossible to stop and study the paintings properly without being pushed over by other visitors. But they are so popular that it’s hard to expect anything other. Through all two weeks weather in Paris was very good, so I could see all the city and meet people living there. They were very kind and friendly to me, especially men. I made there many friends. I want to go back there next year. Maybe you will join me?