a, 5/252

b, 11/90

a)\(=>x=\dfrac{5}{9}:\dfrac{4}{7}=\dfrac{35}{36}\)

b)\(=>x=\dfrac{11}{15}:\dfrac{2}{3}=\dfrac{11}{10}\)

a) \(\dfrac{4}{7}\times x=\dfrac{5}{9}\)

           \(x=\dfrac{5}{9}\div\dfrac{4}{7}\)

          \(x=\dfrac{5}{9}\times\dfrac{7}{4}\)

          \(x=\dfrac{35}{35}\)

b) \(\dfrac{11}{15}\div x=\dfrac{2}{3}\)

     \(x=\dfrac{11}{15}\div\dfrac{2}{3}\)

     \(x=\dfrac{11}{15}\times\dfrac{3}{2}\)

     \(x=\dfrac{33}{30}\)

     \(x=\dfrac{11}{10}\)

\(x=-\dfrac{3}{16}+\dfrac{1}{4}=\dfrac{1}{16}\)

bạn viết rõ đề nhé 

a. \(=\left(\dfrac{12}{15}+\dfrac{3}{15}\right)+\left(\dfrac{4}{3}+\dfrac{5}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)\\ =1+2+1=4\)

b. \(x\times\dfrac{3}{4}=\dfrac{1\times3\times6\times5}{6\times5\times5\times3}\\ x\times\dfrac{3}{4}=\dfrac{1}{5}\\ x=\dfrac{1}{5}:\dfrac{3}{4}\\ x=\dfrac{4}{15}\)

a.

(12/15+3/15)+(4/3+5/3)+(1/4+3/4)

=1+3+1=5

b.X x 3/4=1/5

           X=1/5:3/4

           X=4/15

\(lim\left(50.\dfrac{1-\left(\dfrac{4}{5}\right)^n}{1-\dfrac{4}{5}}+\dfrac{4}{5}.50.\dfrac{1-\left(\dfrac{4}{5}\right)^{n-1}}{1-\dfrac{4}{5}}\right)\) \(=50.\dfrac{1}{\dfrac{1}{5}}+\dfrac{4}{5}.50.\dfrac{1}{\dfrac{1}{5}}=450\)

\(a,\Rightarrow x=\dfrac{7}{3}+\dfrac{6}{7}=\dfrac{49+18}{21}=\dfrac{67}{21}\\ b,\Rightarrow x=\dfrac{15}{7}-\dfrac{13}{14}=\dfrac{30-13}{14}=\dfrac{17}{14}\\ c,\Rightarrow3x=\dfrac{9}{4}-\dfrac{5}{6}=\dfrac{27-10}{12}=\dfrac{17}{12}\\ \Rightarrow x=\dfrac{17}{12}\cdot\dfrac{1}{3}=\dfrac{17}{36}\)

\(x=\dfrac{7}{3}+\dfrac{6}{7}=\dfrac{67}{21}\)

\(x=\dfrac{15}{7}-\dfrac{13}{14}=\dfrac{17}{14}\)

\(x=\left(\dfrac{9}{4}-\dfrac{5}{6}\right):3=\dfrac{17}{36}\)

\(x-\dfrac{6}{7}=\dfrac{7}{3}\\ \Rightarrow x=\dfrac{7}{3}+\dfrac{6}{7}\\ \Rightarrow x=\dfrac{67}{21}\)

\(x+\dfrac{13}{14}=\dfrac{15}{7}\\ \Rightarrow x=\dfrac{15}{7}-\dfrac{13}{14}\\ \Rightarrow x=\dfrac{17}{14}\)

\(\dfrac{9}{4}-3\times x=\dfrac{5}{6}\\ \Rightarrow3\times x=\dfrac{9}{4}-\dfrac{5}{6}\\ \Rightarrow3\times x=\dfrac{17}{12}\\ \Rightarrow x=\dfrac{17}{12}:3\\ \Rightarrow x=\dfrac{17}{36}\)

\(x+\left(13-15\right)=5+\left(10-7\right)\)

\(< =>x-2=8=>x=10\)

Ta có: \(x+\left(13-15\right)=5+10-7\)

\(\Leftrightarrow x-2=15-7=8\)

hay x=10

x + (13 - 15) = 5 + (10 - 7)

x + (13 - 15) = 5 + 3

x + (13 - 15) = 8

x + (-2) = 8

x = 8 - (-2)

x = 10

Chúc bạn học tốt!

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

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

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

\(x=\frac{11}{6}\)

\(8,75.x+1,25.x=26,3\)

\(x.\left(8,75+1,25\right)=26,3\)

\(x.10=26,3\)

\(x=26,3\div10\)

\(x=2,63\)

\(x-4\frac{5}{6}=2\frac{1}{6}+\frac{5}{6}\)

\(x-\frac{29}{6}=3\)

\(x=\frac{47}{6}\)

\(5\frac{4}{5}+x-7\frac{7}{18}=15\frac{3}{4}\)

\(\frac{29}{5}+x-\frac{133}{18}=\frac{63}{4}\)

\(\frac{29}{5}+x=\frac{63}{4}+\frac{133}{18}\)

\(\frac{29}{5}+x=\frac{259}{8}\)

\(x=\frac{259}{8}-\frac{29}{5}\)

\(x=\frac{1063}{40}\)

ĐKXĐ: x ≠ 3, x ≠ 4, x ≠ 5, x ≠ 6.

Ta có:

Vậy phương trình đã cho có nghiệm là x = 0;x = 9/2. 

Bài 1: 

Ta có: \(x-35\%\cdot x=\dfrac{1}{25}\)

\(\Leftrightarrow65\%\cdot x=\dfrac{1}{25}\)

\(\Leftrightarrow x=\dfrac{1}{25}:\dfrac{13}{20}=\dfrac{1}{25}\cdot\dfrac{20}{13}=\dfrac{4}{65}\)

Vậy: \(x=\dfrac{4}{65}\)

Bài 2: 

a) Ta có: \(17\dfrac{2}{31}-\left(\dfrac{15}{17}+6\dfrac{2}{31}\right)\)

\(=17\dfrac{2}{31}-\dfrac{15}{17}-6\dfrac{2}{31}\)

\(=11+\dfrac{2}{31}-\dfrac{15}{17}\)

\(=\dfrac{5366}{527}\)