Think about what the ratio means. There are 17 students for every 3 staff members.
This means that there are 20 people total.
Divide the total number of people present (740) by 20 (the total number of people in the ratio). This gives you 37.
Multiply 37 by 3 (number of faculty members) and 37 by 17 (number of students). You get 111 faculty members, and 629 students.
Hope that helps!