There are 23 girls, which means that there are 19 boys.
  
 We know that 10 girls walk to school, 6 boys cycle to school, and 7 of 11 kids who ride the bus are boys.
  
 So, that leaves 19-13=6 boys walk to school.
  
 6+10=16.
  
 Number of students who walk to school=16 students.