\(A=\dfrac{5}{11}.\dfrac{5}{7}+\dfrac{5}{11}.\dfrac{2}{7}+\dfrac{6}{11}=\dfrac{5}{11}\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{6}{11}=\dfrac{5}{11}.1+\dfrac{6}{11}=\dfrac{5}{11}+\dfrac{6}{11}=\dfrac{11}{11}=1\)

\(B=\dfrac{3}{13}.\dfrac{6}{11}+\dfrac{3}{13}.\dfrac{9}{11}-\dfrac{3}{13}.\dfrac{4}{11}=\dfrac{3}{13}\left(\dfrac{6}{11}+\dfrac{9}{11}-\dfrac{4}{11}\right)=\dfrac{3}{13}.1=\dfrac{3}{13}\)

\(C=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{3}{6}-\dfrac{2}{6}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right).0=0\)

\(A=\dfrac{5}{7}.\dfrac{5}{11}+\dfrac{5}{7}.\dfrac{8}{11}-\dfrac{5}{7}.\dfrac{2}{11}\)

\(A=\dfrac{5}{7}.\left(\dfrac{5}{11}+\dfrac{8}{11}-\dfrac{2}{11}\right)\)

\(A=\dfrac{5}{7}.\dfrac{5+8-2}{11}\)

\(A=\dfrac{5}{7}.\dfrac{11}{11}\)

\(A=\dfrac{5}{7}.1=\dfrac{5}{7}\)

\(B=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{35}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{63}\)

\(B=\dfrac{95}{72}\)

\(C=\dfrac{4^6.9^5+6^9.120}{8^4-3^{12}-6^{11}}\)

\(C=\dfrac{\left(2^2\right)^3.\left(3^2\right)^5+\left(2.3\right)^9.2^3.3.5}{\left(2^3\right)^4.3^{12}-\left(2.3\right)^{11}}\)

\(C=\dfrac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}\)

\(C=\dfrac{2^{12}.3^{10}.\left(1+5\right)}{2^{11}.3^{11}.5}\)

\(C=\dfrac{2.6}{5.3}=\dfrac{12}{15}=\dfrac{4}{5}\)

Lời giải:

$(x-\frac{1}{4}):(\frac{-3}{10}+\frac{7}{12}-\frac{2}{3})$

$=(x-\frac{1}{4}):\frac{-23}{60}=(-1\frac{1}{4}-\frac{1}{4}):\frac{-23}{60}$

$=\frac{-3}{2}: \frac{-23}{60}=\frac{90}{23}$

Chọn B

Lời giải:

a.

$\frac{5}{15}-\frac{1}{6}\times \frac{2}{5}=\frac{5}{15}-\frac{1}{15}=\frac{4}{15}$

b.

$\frac{8}{24}+\frac{3}{4}:\frac{1}{8}=\frac{1}{3}+6=\frac{19}{3}$

c.

$\frac{1}{7}: \frac{2}{8}-\frac{1}{7}=\frac{1}{7}\times 4-\frac{1}{7}$

$=\frac{1}{7}\times (4-1)=\frac{1}{7}\times 3=\frac{3}{7}$

Mn khoanh giúp mk nka !!!

1. C

2. C

3. C

Oh, bn sửa giùm mik nhé

a. \(A=\dfrac{1}{2}\cdot\dfrac{2}{3}+\dfrac{5}{10}\) \(B=\dfrac{7}{8}-\dfrac{1}{4}\cdot\dfrac{3}{2}\)

\(=\dfrac{1}{3}+\dfrac{1}{2}\) \(=\dfrac{7}{8}-\dfrac{3}{8}\\ =\dfrac{1}{2}\)

\(\Rightarrow A>B\)

b. \(C=\dfrac{2}{3}\cdot\dfrac{4}{5}+\dfrac{8}{15}-\dfrac{1}{15}\)

\(=\dfrac{8}{15}+\dfrac{7}{15}\\ =\dfrac{15}{15}\\ =1\)

\(D=\dfrac{1}{2}\cdot\dfrac{5}{6}+\dfrac{2}{3}\cdot\dfrac{3}{4}\)

\(=\dfrac{5}{12}+\dfrac{6}{12}\\ =\dfrac{11}{12}\)

\(\Rightarrow C>D\)