Mike observed that 75% of the students of a school liked skating. if 35 students of the school didn't like skating, the number of students who liked skating was

Cross multiply.

75 / x = 25 / 35
   25x = 35(75)
   25x = 2625
   /25     /25
       x = 105

Therefore 105 students liked skating.

Proof:

105 + 35 = 140.
140 * 0.75 = 105
140 * 0.25 = 35

140 (total) split into quarters.

35 + 35 + 35 + 35 = 140
35 + 35 + 35 = 105 (3 quarters liked)
35 = 35 (1 quarter disliked)

For me i think it'll land on blue