f.2 maths 1題20分

Let x be the number of adults and y be the number of students
x+y=250(1)
50x+20y=6800(2)
From(1), x=250-y(3)

Put (3) into (2),
50x+20y=6800
50(250-y)+20y=6800
12500-50y+20y=6800
-30y= -5700
y=190

Put y=190 into (1)
x+y=250
x+190=250
x=60
So there are 60 adults and 190 students who attend the concert.

Let X be the number of adults
Let Y be the number of students

X+Y = 250 --- (1)
50X+20Y = 6800 --- (2)

By (1),
X= 250-Y

Sub (1) into (2)
50(250-Y) + 20Y = 6800
12500 - 50Y + 20Y = 6800
12500 - 30Y = 6800
30Y = 12500-6800
30Y = 5700
Y = 190

Sub Y=190 into (1)
X = 250-190
X = 60

Therefore, number of audlts is 60 and number of students is 190

你呢條應該係咁做既

Let the no. of adults and students be x and y respectively,

x+y=250 -------------1
50x+20y=6800 -----2

1 x 20 : 20(x+y) = 20(250)
20x+20y=5000 -------3

2 - 3 : (50x+20y)-(20x+20y)=6800-5000
50x+20y-20x-20y=1800
30x=1800
x=60


Put x=60 in 1,
x+y=250
60+y=250
y=190

The no. of adults and students are 60 and 190 respectively.

Let x be no of adults&y be no of students
x+y=250...(1)
50x+20y=6800...(2)
50(250-y)+20y=6800
12500-50y+20y=6800
30y=5700
y=190
x=60

let: (250-x) = Adults
x = Student

so: 50*(250-x)+20*x = 6800


Adults : 60
Students : 190