Final answer:
Bill Clinton was in his late 40s to early 50s during his affair with Monica Lewinsky.
Step-by-step explanation:
During his affair with Monica Lewinsky, Bill Clinton was in his late 40s to early 50s.
The affair took place between 1995 and 1997, so Clinton would have been around 49 to 51 years old at that time.
The affair became widely known in 1998 when it was reported by the media.