Question

I said to him, " How did you get this formula?​

Answer 1

Answer:

I told him how did he get that formula.

said to changes to told in reported speech.

Answer 2

Reported speech:-" I asked him that if he got that formula."

Mate, here I changes to he, this changes to that , since u r asking a question it becomes I asked

Also never forget to put inverted commas

Present tense changes to past tense.

Hope u understood!