Question

what is the percentage of students that reported skating as their favorite activity?
jogging:12%
walking:60 students
biking:25%
skating:210 students
other:108 students

Answer 1

percentage left = 100-(12+25) = 63%

percentage of skating out of walking, skating and other:
(210)/(60+210+108) = 5/9

percentage of skating = (5/9) * 63 = 35%

Answer 2

To find the total students do:
60+210+108 = 278 total students

Now use this equation to get the percentage:
part/whole *100
210 students/278 students *100
0.7554 *100
=75.54 %