A walk in the park

If something is “a walk in the park,” it is very easy to do. Taking the pills isn’t exactly “a walk in the park,” either. Taking the pills isn’t easy to do. She has been running marathons for years, so this 5K should be “a walk in the park” for her, or the 5K should be easy for her to do. High school classes were “a walk in the park” compared to college level courses.