救命！！！！！！！！！！！二十點家！好煩呀！

1.
2[a-(1-a)]=3(a-1)+8
2(a-1+a)=3a-3+8
2a-2+2a=3a-5
4a-2=3a-5
4a-3a=-5+2
a=-3

2.
5m+3=9-4m
5m+4m=9-3
9m=6
m=6/9

3.
2x=3(1-x)-(x+1)
2x=3(1-x)-x-1
2x=3-3x-x-1
2x+3x+x=3-1
6x=2
x=1/3

4.
k/30+5=k/10
k/30-k/10=-5
k/30-3k/30=-5
(k-3k)/30=-5
-2k/30=-5
-2k=-150
k=-150/-2
k=75

5.
9(2a-1)=3[4(1+2a)-5]-8a
18a-9=3(4+8a-5)-8a
18a-9=3(8a-1)-8a
18a-9=24a-3-8a
18a-24a+8a=-3+9
2a=6
a=3

6.
1/3(t+9)=1/3-0.5(t+3)
t/3+9/3=1/3-0.5t-1.5
t/3+9/3=-0.5t-3.5/3
t/3+0.5t=-3.5/3-9/3
(1/3+0.5)t=-12.5/3
(2.5/3)t=-12.5/3
t=(-12.5/3)/(2.5/3)
t=-12.5/2.5
t=-5

2009-08-14 19:06:59 補充：
7.
(2n-5)/3=(n-10)/9
2n/3-5/3=n/9-10/9
2n/3-n/9=-10/9+5/3
6n/9-n/9=-10/9+15/9
(6n-n)/9=(-10+15)/9
5n/9=5/9
n=1

8.
(x-1)/2=(x+1)/3+1
x/2-1/2=x/3+1/3+1
x/2-x/3=1/3+1/2+1
3x/6-2x/6=2/6+3/6+6/6
x/6=11/6
x=11

2009-08-14 19:07:41 補充：
9.
7u-(4u-1)/2=21
7u-2u+1/2=21
7u-2u=21-1/2
5u=20.5
u=4.1

10.
(2-t)/4-t=(2t-3)/5
1/2-t/4-t=2t/5-3/5
-t/4-t-2t/5=-3.5-1/2
-5t/20-20t/20-8t/20=-4
(-5t-20t-8t)/20=-4
-33t/20=-4
-t=-4/33*20
-t=-80/33
t=80/33

2009-08-14 19:18:21 補充：
11.
Let the speed of the slower train be x km/h.
Then the speed of the other train=2x km/h.
In 5 hours,distance travelled by slower traim= x km/h × 5h =5x km
Distance travelled by faster train= 2x km/h × 5h =10x km
Given,total distance=600 km

2009-08-14 19:19:25 補充：
Distance travelled by faster train= 2x km/h × 5h =10x km
Given,total distance=600 km

Therefore,
5x+10x=600
15x=600
x=40

The speed of the slower train
=40 km/h

The speed of the faster train
=80 km/h

Therefore,the speeds of the trains are 40km/h and 80km/h

方程唔係好識答，英文就題就ok。
Ans.
Two men are approaching each other from towns 600km apart.One man's speed is one-hundred times the other man's speed.They crash each other after 5 century.Find when they crash.
In this problem,we don't need to do:
sperm shooting distance=(*****ing speed)x1.5 x (*****ing time)x0.5
first sperm shooting distance+second sperm shooting distance=total sperm shooting distance
Let the speed of the slower man of the penis be x km/s.
Then the speed of the other penis=___xxkm/s_____.
In 5 centuries,distance travelled by slower man=------------ x ---------=----------km
Distance travelled by faster man=----x-------x-------x--------=----x^2------km
Given,total sperm shooting distance=-------3x------km
Therefore,--x---+-3x----=-----4x-------
=4x
=4x
Therefore,the *****ing speeds of the men are ---x----km/h and ---x-----km/h