There were 100 people in attendance at the school dance. Ten percent of the attendees were school faculty and staff. Of the remaining attendees, two-thirds were girls. How many boys attended the school dance? Let's be accurate as possible.
Of 100 people in attendance at the school dance, 10% were school faculty and staff, or a total of 0.1 * 100 = 10 people. This leaves 100 - 10 = 90 students in attendance. Of the remaining attendees, two - thirds were girls, or (2 / 3) * 90 = 60 attendees were girls. Thus, the remaining 90 - 60 = 30 students were boys who attended the school dance.
The answer: 30.