Answer:
1/10
Explanation:
Okay so, if you convert the fractions so they're both over ten, you have 2/10 and 7/10, adding those together you get 9/10 of the student population; leaving 1/10 of the students left. So the answer is 1/10 of the students ride the bus to school.
(Unless I completely read this question wrong lol, hope this helped some.)