My five year old step son does not behave properly with me and answers me back. My wife does not like me scolding her. What do I do?

I don't think scolding doesn't help when a kid answers back, be it your biological kid or a step kid. You have to be patient and wait for the right moment to tell the kid that he was wrong. Now that you are new to his family structure, you need to give him time. Let him accept you as a well-wisher, a friend and a father, and things will fall in place. Do not rush into things, as it can dent your relationship with him for life. You can go out for outings with him, to see matches or all boys' thing and this will help you bond with him.