其它
On average, each student has $$14$$ balls. Each of the $$15$$ girls has $$24$$ balls on average. There are $$25$$ boys, and their average number of balls is~\uline{~~~~~~~~~~}~. 
Overseas Competition->Knowledge Point->Word Problem Modules->Average Problems 
$$14\times(15+25)=560$$  $$560-15\times24=200$$  $$200\div25=8$$ 