so assuming that each student chose only one sport or 'other', add the percents and subtract from 100
37.5+40=77.5
100-77.5=22.5
22.5%=other
18 students=22.5%
divide both sides by 22.5
0.8=1%
therfor
100%=80
80 students participated
futbol=37.5% of 80=0.375 times 80=30
30 picked football