~數學難題~Help

X adults, (100-X) children

No. of apples:
3 X + (1/3) (100 - X) = 100
9 X + (100 - X) = 300
8 X = 200
X = 25
So, there are 25 adults.

設 : 大人有x個, 小孩有y個,

(a) x+y=100
(b)3x+ (1/3)y =100

(b)方程x3, 化簡為 9x+y=300----------(c)

(c)方程 - (a)方程得 :
9x-x+y-y=300-100
8x=200
x=25 (人)
大人有25個。
即小孩有100-25人=75人

大人=x
小孩=y
x+y=100
3x+y/3=100
x=100-y
3(100-y)+y/3=100
300-3y+y/3=100
300-9y/3+y/3=100
300-8y/3=100
300=100+8y/3
300-100=8y/3
200=8y/3
200*3/8=8y/3*3/8
75=y
y=75

25*3+75/3
=75+25
=100


大人=25
小孩=75