有100个人,有100块饼,大人一个人吃三块,三个小孩吃一块饼,问有几个小孩,

3x + y/3 = 100
x+y = 100
x = 100 - y
3(100-y) + y/3 = 100
900 - 9y + y = 300
600 - 8y = 0
600 = 8y
y = 75
x = 100-y - 25
75个小孩
大人25个