S1 Math (Algebra 3)

1.
The distance travelled by the second be xkm
so the distance travelled by the first bus is 2x-30km
x+2x-30=336
3x-30=336
3x=366
x=122
so the distance travelled by the second is 122km.
and the distance travelled by the first bus is 214km. <------2(122)-30km

2.a
an expression for her weekly earnings:
30(45)+30(2)(x)
=1350+60x

2.b
1350+60x=1800
60x=450
x=7.5
if she earns $1800 each week , the value of x is 7.5

2007-12-28 20:48:05 補充：
如果睇唔明在補充講邊到唔明...我再詳細教你~~

1. Let x km be the distance the first bus traveled,
and y km be the distance the second traveled.

x = 2y - 30----------------------(1)
x + y = 336---------------------(2)

From (2),
x = 336 - y----------------------(3)

Sub (3) into (1),
336 - y = 2y - 30
3y = 336 + 30
3y = 366
y = 122

Sub y = 122 into (3),
x = 336 - 122
x = 214

Therefore, the first bus has traveled 214 km while the second 112 km.

2. a. 45(30) + 2(30)x
=1350 + 60x

b. If she earns $1800 each week,
1350+ 60x = 1800
60x = 1800 - 1350
x = 7.5