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We have not understood the query that you have posted. We would request you to clarify / provide additional details so that we may answer this to the best of the ability.

Pl. check the first statement. the sum of a 3 digit number  can't  be 17.It may be that the sum of the digits of a 3 digit number is 17.

Next, if  the  middle digit exceeds the other digits by 1 then both of the other digits must be same. So the reversed number will also come out to be the same.