Let the number of students studying in school be x.
Number of students coming by car:
=25×x=25x
Number of students coming by bus:
=14×x=14x
Remaining students walk to school
=x−(25x+14x)=x−(8x+5x20)
=x−13x20=20x−13x20=7x20
Now, number of students who walk to school on their own:
=13 of 7x20=7x60
Since, 224 students come to school on their own.
According to the question
⇒7x60=224⇒x=224×607⇒x=32×60=1920
Hence, 1920 students study in that school.