4. In the fourth grades of School No. 15, 100 students are studying. 37 of them have enrolled in the football section, 40 - in the swimming section, 15 people have enrolled in both sections. How many students have not enrolled in any section?
4. 5) $40-15=25$ (students) - enrolled only in the swimming section;
2) $37-15=22$ (students) - enrolled only in the football section;
3) $25+22+15=62$ (students) - enrolled in the football and tennis sections;
4) $100-62=38$ (students) - did not enroll in any section.

Answer: 38 students did not enroll in any section.