###Human: 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?, ### Assistant: 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. 
 So the answer is :  30