Please explain and solve this problem for me. Thanks in advance.

Look at attachment. has all info needed. need

Identify the type of observational study described. a statistical analyst obtains data about ankle injuries by examining a hospital's records from the past 3 years. cross-sectional retrospective prospective

65% of students in your school participate in at least one after school activity. if there are 980 students in you school, how many do not participate in an after school activity?