解方程（快）---10點

1.....x+2x+9=90
3x+9=90
3x=81
x=27

2.....2(4x+x)=120
10x=120
x=12

3.....x+(x-1)+(x-2)=192
x+x-1+x-2=192
3x-3=192
3x=195
x=65

4.....3x-5=(x-5)4
3x-5=4x-20
x=15

5.....x+x-9=77
2x=86
x=43


6.....x+3x+3x/2=1540
4x+3x/2=1540
8x+3x=3080..............................一齊乘2
11x=3080
x=280


以上題目 全按照"先乘除,後加減" ,這鐵則運算

1.....x+2x+9=90
Sol: x+2x+9=90
3x=90
x=90/3
x=30 (Answer)

2.....2(4x+x)=120
Sol: 2(4x+x)=120
5x=120/2
5x=60
x=60/5
x=12 (Answer)

3.....x+(x-1)+(x-2)=192
Sol: x+(x-1)+(x-2)=192
3x-3=192
3x=195
x=195/3
x=65 (Answer)

4.....3x-5=(x-5)4
Sol: 3x-5=(x-5)4
3x-5=4x-20
3x-4x=-20+5
-x = -15
x=15 (Answer)

5.....x+x-9=77
Sol: x+x-9=77
2x = 77+9
2x = 86
x = 86/2
x= 43 (Answer)

6.....x+3x+3x/2=1540
Sol: x+3x+3x/2=1540
2(x+3x+3x/2)=2(1540)
2x+6x+3x=3080
11x=3080
x=3080/11
x=280 (Answer)

2008-11-25 22:44:25 補充：
Sorry 更正題一:
1.....x+2x+9=90
3x=81
x=81/3
x=27 ( Answer)

1) x+2x+9=90
3x=81
x=27

2) 2(4x+x)=120
8x+2x=120
10x=120
x=12

3) x+(x-1)+(x-2)=192
3x-3=192
3x=195
x=65

4) 3x-5=(x-5)4
3x-5=4x-20
x=15

5) x+x-9=77
2x-9=77
2x=86
x=43

6) x+3x+3x/2=1540
(2x+6x+3x)/2=1540
11x=3080
x=280

First , x+ 2x =3x
so... 3x+9=90
3x=81......and then think it your self

Second 2(5x)=120
5x= 120/2
5x=60......adn then....
Third x+(x-1)+(x-2)=192
first tkae away the 括號..LOOK 　at the （　＋）號ＢＥＦＯＥ and then 與括號的比較
+-正負得負 = -
so x+x-1+x-2(because it 本身 (-) , so no need to change it)
but e.g x-(x+1)-(x+2) will change to -> x-x-1-x-2(正負得負)
continus...x+x-1+x-2 = 192
x+x+x-1-2=192
3x=192+3
......
four 3x-5=(x-5)4
3x-5 = 4x-20(先把括號的數乘4)
-5+20=4x-3x
........

five and six ....think it your self

Don't just copy the answer...you must try to do..
you never try.. u never know

1.

圖片參考：http://f20.yahoofs.com/hkblog/BBT9wtCRERvx3HLEBB_jneqgOZyV_2/blog/ap_20081125081438657.jpg.jpg?ib_____DOV_U1jXp


2. 2(4x+x)=120
10x=120 x=12
3.


圖片參考：http://f20.yahoofs.com/hkblog/BBT9wtCRERvx3HLEBB_jneqgOZyV_2/blog/ap_20081125081446125.jpg.jpg?ib_____D3JFPD_ca


4.

圖片參考：http://f20.yahoofs.com/hkblog/BBT9wtCRERvx3HLEBB_jneqgOZyV_2/blog/ap_20081125081453485.jpg.jpg?ib_____D4_HSCzPj

5.


圖片參考：http://f20.yahoofs.com/hkblog/BBT9wtCRERvx3HLEBB_jneqgOZyV_2/blog/ap_20081125081500290.jpg.jpg?ib_____DLHpG13Mt


6.


圖片參考：http://f20.yahoofs.com/hkblog/BBT9wtCRERvx3HLEBB_jneqgOZyV_2/blog/ap_20081125081507588.jpg.jpg?ib_____DyYvUtQ5Y

1.x+2x+9=90
x+2x=81
3x=81
x=27

2.2(4x+x)=120
4x+x=60
5x=12

3.x+(x-1)+(x-2)=192
x+x-1+x-2=192
3x-3=192
3x=195
x=65

4.3x-5=(x-5)4
3x-5=4x-20
3x-4x=-20+5
-x=-15
x=15

5.x+x-9=77
2x-9=77
2x=77+9
2x=86
x=43

6.x+3x+3x/2=1540
4x+1.5x=1540
5.5x=1540
x=280

2008-11-25 20:15:51 補充：
Sorry
Q.2 answer:
x=12

1. x+2x+9=90

3x+9 =90

3x=81

x=27

2. 2(4x+x)=120

8x+2x=120

10x=120

x=12

3. x+(x-1)+(x-2)=192

x+x+x-1-2=192

3x=192+1+2

3x=195

x=65

4. 3x-5=4(x-5)

3x-5=4x-20

-x=-15

x=15

5. x+x-9=77

2x-9=77

2x=86

x=43

6. x+3x+3x/2=1540

2x+6x+3x=3080 整條式乘2

11x=3080

x=280

1).x+2x+9=90
3x=90-9
3x=81
x=27

2).2(4x+x)=120
4x+x=60
5x=60
x=12

3).x+(x-1)+(x-2)=192
x+x-1+x-2=192
3x=192+1+2
3x=195
x=65

4).3x-5=(x-5)4
3x-5=4x-20
x=15

5).x+x-9=77
2x=77+9
2x=86
x=43

6).x+3x+3x/2=1540
2x/2+6x/2+3x/2=1540
11x/2=1540
11x=3080
x=280

1.....x+2x+9=90
...........3x+9=90
...............3x=90-9
...............3x=81
.................x=27

2.....2(4x+x)=120
...........2(5x)=120
.............10x=120
.................x=12

3.....x+(x-1)+(x-2)=192
............x+x-1+x-2=192
.....................3x-3=192
........................3x=192+3
........................3x=195
..........................x=65

4.....3x-5=(x-5)4
.......3x-5=4x-20
.....3x-4x= -20+5
...........-x= -15
............x=15

5.....x+x-9=77
.............2x=77+9
.............2x=86
...............x=43

6.....x+3x+3x/2=1540
.................7x/2=1540
.................3.5x=1540
......................x=440