มีกี่ประตูที่ทำได้เมื่อคะแนนน้อยกว่า 13 ชนะน้อยกว่า 3 และประตูน้อยกว่า 15
How many goals against were scored when the points were smaller than 13, the wins were smaller than 3, and the goals for were smaller than 15?
df = pd.DataFrame(columns=['goals_against', 'goals_for', 'points', 'wins'])
df[(df['points'] < '13') & (df['wins'] < '3') & (df['goals_for'] < '15')]['goals_against'].sum()