I need to know if the deductive reasoning that is used in this example is affirming the hypothesis or denying the conclusion. If a number is divisible by 3, then the sum of the digits of that number is divisible by 3. A number is divisible by 3. Therefore the sum of the digits of that number is divisible by 3. I think that it is denying the conclusion. Is this right?

No, it is not right.