Letter Writing is not a difficult task if you understand the format. Below is a sample of letter which can be used while writing to a brother guidance about HSC Subject (and other such informal letters)
You can edit the information in blue with details appropriate for you .
(Write your name here),
Brother Name, ,
Dear brother (name),
Hope you are doing good. How are your studies going on? I heard that you have received a good ranking on your college exams. I received your previous letter last month inquiring about me and my studies. I am doing well in my exams. How are aunt, uncle, and your sister? Hope they are fine. I am planning a trip to Mumbai next month after my vacation classes. I wish to meet you all during the holidays. We can have fun.
Now my 10th board exams have been completed. I am waiting for the result. I assure you I will certainly score good marks, probably above 90 percent. I need your suggestions and guidance to take on my HSC group in the next academic year. I am wishing to go on for medicine in my higher studies. So I wish to know which HSC subjects would be the best to choose from. Also, I am a little lagging behind in my mathematics subject and more interested in science-related subjects. Should I go for bio-math, computer or science subjects? I also wish to have a good knowledge of computers as it would be trending in the future. So please do suggest me what you think would be appropriate to choose in this regard. I wish you to guide me.
And thank you for the gift you have sent me. I loved it. Take care of your health. Convey my regards to everyone at home as well. We shall meet soon on the vacation.