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

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

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

\(\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}\)                                    \(\frac{3}{5}.\frac{2}{8}+\frac{-6}{16}.\frac{2}{5}+\frac{-6}{15}:\left(-16\right)\)

\(=\frac{-5}{7}\left(\frac{2}{11}+\frac{9}{11}\right)\)                                 \(=\frac{3}{20}+\frac{-3}{20}+\frac{1}{40}\)

\(=\frac{-5}{7}.1=\frac{-5}{7}\)                                       \(=0+\frac{1}{40}=\frac{1}{40}\)

\(x-\frac{2}{5}=0,24\)                                           \(\left(\frac{7}{3}x-0,6\right):3\frac{2}{5}=1\)

\(\Rightarrow x=0,24+\frac{2}{5}=\frac{16}{25}\)                         \(\Rightarrow\left(\frac{7}{3}x-0,6\right):\frac{17}{5}=1\)

vậy x = 16/25                                                       \(\Rightarrow\frac{7}{3}x-0,6=\frac{17}{5}\)

                                                                          \(\Rightarrow\frac{7}{3}x=\frac{17}{5}+0,6=4\)

                                                                           \(\Rightarrow x=4:\frac{7}{3}=\frac{12}{7}\) 

                                                                           vậy x = 12/7

\(\left(6\div\dfrac{3}{5}-1\dfrac{1}{6}\times\dfrac{6}{7}\right)\div\left(4\dfrac{1}{5}\times\dfrac{10}{11}+5\dfrac{2}{11}\right)\)

\(=\left(6\times\dfrac{5}{3}-\dfrac{7}{6}\times\dfrac{6}{7}\right)\div\left(\dfrac{21}{5}\times\dfrac{10}{11}+\dfrac{57}{11}\right)\)

\(=\left(10-1\right)\div\left(\dfrac{210}{55}+\dfrac{57}{11}\right)\)

\(=9\div9\)

\(=1\)

ai lm tr mình cho tích

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

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

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

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

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

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

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

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

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

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

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

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

3:

3/5:x=3

=>x=3/5:3=1/5

4:

a:

=1/5+4/5+4/11+7/11=1+1=2

b: =5/6+5/9-1/4

=30/36+20/36-9/36

=41/36

5: Tổng hai số là 100

Số bé là 100*2/5=40

Số lớn là 100-40=60

=9.

=139/11.

a) 6:3/5-11/6 x 6/7

= 10-11/7

= 59/7

b)41/5 x 10/11+ 5 2/11

= 82/11+ 57/11

= 139/11

=9.

=139/11.