I have received a letter with four separate questions that are numbered from 1 thru 4. Now, I am going to prepare a reply letter and intend to provide my answers to each of these questions. Would you please share with me how to write an introductory sentences telling that my number one answer is for question one, and so on.
Let me answer your questions in the order you asked them.
Let me answer your questions in the order they were asked.
But, if the questions are fairly different from one another, you can simply say "Let me address your questions one at a time" and then number them accordingly. The context will make it perfectly clear you are answering the questions in the original order.
You can go with following introductory sentences telling that your number one answer is for question one, and so on:
"Thanks for your questions. I give below the answers to your questions in seriatim: