Can you thoroughly explain the process of getting the answer

In a city with three high schools, all the ninth graders took a Standardized Test, with these results: High School Number of ninth graders (Frequency) The city's PR manager, who never took statistics, claimed the mean score of all ninth graders in the city was the average of 76, 93, and 70, which is 79.7. Of course, that is incorrect. What is the mean score for all ninth graders in the city? Round to one decimal place. mean of all ninth grader's scores = Question Help: 8 Message instructor Submit