a) x + 285 = 2094

       x = 2094 - 285

       x = 1809

b) x - 45 = 5605

      x = 5605 + 45

      x = 5650

c) 6000 - x = 2000

             x = 6000 - 2000

             x = 4000

215+7(x+1)=250

7(x+1)=250-215

7(x+1)=35

x+1=35:7

x+1=5

x=5-1=4

Vậy x=4

\(215+7\left(x+1\right)=250\)

\(\Leftrightarrow7x+7=250-215\)

\(\Leftrightarrow7x+7=35\)

\(\Leftrightarrow7x=35-7\)

\(\Leftrightarrow7x=28\)

\(\Leftrightarrow x=28:7\)

\(\Leftrightarrow x=4\)

a) 1996 + x = 2002

      x = 2002 - 1996

      x = 6

b) x x 3 = 9861

      x = 9861 : 3

      x = 3287

c) x : 4 = 250

      x = 250 x 4

      x = 1000

\(x-0,27=\frac{\frac{73}{77}+\frac{73}{165}+\frac{73}{285}}{25.\left(\frac{5}{84}+\frac{3}{180}+\frac{4}{285}\right)}\)

\(x-\frac{27}{100}=\frac{73.\left(\frac{1}{77}+\frac{1}{165}+\frac{1}{285}\right)}{25.4.\left(\frac{5}{4.84}+\frac{3}{4.180}+\frac{4}{4.285}\right)}\)

\(x-\frac{27}{100}=\frac{73.\left(\frac{2}{105}+\frac{1}{285}\right)}{100.\left(\frac{5}{336}+\frac{1}{240}+\frac{1}{285}\right)}\)

\(x-\frac{27}{100}=\frac{73.\left(\frac{2}{105}+\frac{1}{285}\right)}{100.\left(\frac{2}{105}+\frac{1}{285}\right)}\)

\(x-\frac{27}{100}=\frac{73}{100}\)

\(x=\frac{73}{100}+\frac{27}{100}\)

\(x=1\)

Vậy x=1

a)Ta thấy:

\(\left|x\right|\ge0\)

\(\Rightarrow\left|x\right|+10\ge0+10=10\)

\(\Rightarrow A\ge10\).Dấu "=" <=>x=0

Vậy Amin=10 <=>x=0

b,c phân tích ra làm tương tự

x : ( 2400 : 30 ) = 560 : 280

x : 80 = 2

x = 2 * 80             => x = 160       (câu a)

a, x: [2400:30] = 560 : 280

x : 80 = 2

x = 160

b,225 : x = 390 : 130

225 : x = 3

x=75