\(a,2\frac{x}{7}=\frac{75}{35}\)

\(\frac{75}{35}=2\frac{5}{35}=2\frac{1}{7}\)

\(\Rightarrow x=1\)

\(b,47:4=...\left(+3\right)\)

     \(\Rightarrow\left(47-3\right):4=11\)

      \(\Rightarrow x=11\)

\(c,\frac{112}{5}=\frac{336}{15}=22\left(+6\right)\)

     \(\Rightarrow x=22\frac{x=6}{15}\)

\(d,7,5x=\frac{75x}{100}:\left(9-6\frac{13}{21}\right)=2\frac{13}{25}\)

     \(\frac{75x}{100}:\left(9-\frac{139}{21}\right)=\frac{63}{25}\)

       \(\frac{75x}{100}:\frac{50}{21}=\frac{63}{25}\)

           \(\Rightarrow\frac{63^3}{25^{\left(1\right)}}\cdot\frac{50^{\left(2\right)}}{21^1}=6=\frac{6}{1}\)

             \(\Rightarrow\frac{6}{1}=\frac{600}{100}\)

Con d sai đề

a) \(\left(x+\frac{1}{4}\right)^2+\frac{11}{25}=\frac{18}{25}\)

\(\Rightarrow\left(x+\frac{1}{4}\right)^2=\frac{7}{25}\)

\(\Rightarrow\) Không có x

Câu a) \(a+x=7\) . Chuyển vế \(a\) ta được :\(x=7-a\)

Câu b) \(a-x=25\) . Chuyển vế \(x\) và 25 ta được : \(a-25=x\) . Vậy \(x=a-25\) .

a) \(a+x=7\)\(\Rightarrow x=7-a\)

b) \(a-x=25\Rightarrow x=a-25\)

\(\frac{2}{3}x-\frac{1}{2}=\frac{1}{10}\)

\(\frac{2}{3}x\)            = \(\frac{1}{10}+\frac{1}{2}\)

\(\frac{2}{3}x\)            =          \(\frac{3}{5}\)

     \(x\)             =     \(\frac{3}{5}:\frac{2}{3}\)

     \(x\)             =         \(\frac{9}{10}\)

Câu b:

(2 4/5x - 50) : 2/3 = 51

2 4/5x - 50 = 51 x 2/3

14/5x - 50 = 34

14/5x = 34 + 50

14/5x = 84

x = 84 : 14/5

x = 30

Vậy x = 30

\(x⋮12;25;30\Rightarrow x\in BC\left(12;25;30\right)\)

\(12=2^2.3;25=5^2;30=2.3.5\)

\(BCNN\left(12;25;30\right)=2^2.3.5^2=300\)

\(BC\left(12;25;30\right)=B\left(300\right)\)

\(B\left(300\right)=\left\{0;300;600;....\right\}\)

\(0\le x\le500\Rightarrow x=300\)

\(\left(3x-2^4\right).7^3=2.7^4\)

\(\left(3x-16\right)=2.7\)

\(3x-16=14\)

\(3x=30\)

\(x=10\)

\(\left|x-5\right|=16+2.\left(-3\right)\)

\(\left|x-5\right|=10\)

\(\Leftrightarrow x-5=10\Rightarrow x=15\)

\(\Leftrightarrow x-5=-10\Rightarrow x=-5\)

1. \(x=\frac{61}{42}\)

2. \(x=\frac{-36}{5}\) 

3. \(x=\frac{13}{11}\)

4. \(x=\frac{1}{12}\)

5.\(x=\frac{-5}{2}\)

\(1,\)\(x-\frac{3}{5}=\frac{3}{35}-\frac{-7}{6}\)

        \(x-\frac{3}{5}=\frac{3}{35}+\frac{7}{6}\)

        \(x-\frac{3}{5}=\frac{263}{210}\)

                    \(x=\frac{263}{210}+\frac{3}{5}\)

                    \(x=\frac{389}{210}\)

        VẬY: \(x=\frac{389}{210}\)

1. \(\frac{25}{100}x+x-\frac{1}{5}x=\frac{1}{5}\)

\(\Leftrightarrow\frac{1}{4}x+x-\frac{1}{5}x=\frac{1}{5}\)

\(\Leftrightarrow\left(\frac{1}{4}+1-\frac{1}{5}\right)x=\frac{1}{5}\)

\(\Leftrightarrow\frac{21}{20}x=\frac{1}{5}\)

\(\Leftrightarrow x=\frac{1}{5}:\frac{21}{20}\)

\(\Leftrightarrow x=\frac{4}{21}\)

Chút nữa tớ làm cho