Well, in percentages, Other = 100% - 40% - 37,5% = 22,5%
In numbers, Other = 18.
If 18___22.5%=0.225
Then x___100%=1
So x = (18*1)/0.225 = 18/0.225 = 80, and 80 is the first answer, the number of students participated.
For second question, which is how many chose football, we have:
x_____37.5%=0.375
18____22.5%=0.225
x = (18* 0.375) / 0.225 = 30
The second answer is 30.
