At football training 3/10 of the players ride a bike, 20% walk to training and the remaining 15 players are driven by their parents.

How many players attend training?

30 players attend training. 3/10 is equal to 30%+20% accounts for 50% of the population. There are 15 people in the remaining 50%, so the other 50% will be 15 as well. 15=15=30