The phrase "fixes upon" means to focus or concentrate on something. There are several synonyms for this phrase, including "zeroes in on," "homes in on," "locks onto," "pays attention to," "directs one's gaze toward," and "targets." Each of these synonyms conveys a sense of purposeful attention or concentration on a particular subject or object. Whether you are studying for an exam, trying to solve a problem, or simply observing the world around you, using a variety of synonyms for "fixes upon" can help you to express yourself clearly and effectively.