1)   50x50=2500

( x+50).50=2500+50=2550

 x+50      =2550:50=51

 x           =51-50=1

(x-2005).2006 = 0

x-2005 = 0:2006

x-2005 = 0

x = 0+2005

x = 2005

480+45.4 = (x+125):5+260

48+180 = x:5+125:5+260

228 = x:5+285

228-285 = x:5

-57 = x:5

-57.5 = x

-285 = x

480 + 180 = ( x + 125 ) : 5 + 260

( x + 125 ) : 5 + 260 = 660

( x + 125 ) : 5 = 660 - 260 = 400

x + 125 = 400 . 5 = 2000

x = 2000 - 125 = 1875 

480+180=(x+125):5+260

(x+125):5+260=660

(x+125):5=400

x+125=2000

x=1875

480+45.4=(x+125):5+260

660=(x+125):5+260

400=(x+125):5

x+125=2000

x=1875

a)(x-2005).2006=0

=>x-2005=0

=>x=2005

b)480+45.4=(x+125):5+260

=>480+180=(x+125):5+260

=>660=(x+125):5+260

=>(x+125):5=400

=>x+125=2000

=>x=1875

c)2005.(x-2006)=2005

=>x-2006=1

=>x=2007

d){(x+50).50-50}:50=50

=>(x+50).50-50=2500

=>(x+50)*50=2550

=>x+50=51

=>x=1

xem lại cái đề bài đầu tiên với

[(x+50).50-50]:50=50

      (x+50).50-50=50.50

      (x+50).50-50=2500

           (x+50).50=2500+50

           (x+50).50=2550

                 x+50=2550:50

x+50=51

x=51-50

x=1

đúng mà 

??????????

mk nhầm đọc ko kĩ đề nhân 4 tưởng nhân 2^^

\(\text{480+45.4=(x+125):5+260 }\\ \left(x+125\right):5+260=660\\ \left(x+125\right):5=660-260=400\\ x+125=400.5=2000\\ x=2000-125=1875\)

\(\text{480+45.4=(x+125):5+260 }\\ \left(x +125\right):5+260=570\\ \left(x+125\right):5=570-260=310\\ \left(x+125\right)=310.5=1550\\ x=1550-125=1425\)

GIẢI

480 + 45 . 4 = (x+125) : 5 + 260

<=> (x+125) : 5 + 260 = 660

<=> (x+125) : 5 = 660 - 260 = 400

<=> x + 125 = 400 . 5 = 2000

<=> x = 2000 - 125

<=> x = 1875

480+180=(x+125):5+260

(x+125):5=660-260

x+125=400*5

x=2000+125

x=2125