For a question like this, all you have to do is remember that a percentage is simply a fraction expressed as a decimal. So, all we have to do is:
[tex] \frac{187}{550} [/tex], and then multiply our decimal answer by 100 to get the percentage:
[tex] \frac{187}{550}[/tex] = 0.34
0.34 x 100 = 34
Therefore 34% of the students walk to school.
I hope this helped and remember to please try and understand the maths that got the answer, not just writing the answer down :))