\(\frac{2}{3}.\frac{4}{7}=\frac{8}{21}\)

\(\frac{3}{11}.2=\frac{6}{11}\)

\(4.\frac{2}{7}=\frac{8}{7}\)

\(\frac{8}{21}:\frac{2}{3}=\frac{8}{21}.\frac{3}{2}=\frac{21}{2.21}=\frac{1}{2}\)

\(\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)

\(\frac{3}{7}:\frac{3}{7}=\frac{3}{7}.\frac{7}{3}=\frac{21}{21}=1\)

lỡ tay bấm gửi trả lời luôn

\(\frac{2}{3}.\frac{1}{6}.\frac{9}{11}=\frac{2.9}{18.11}=\frac{2.9}{2.9.11}=\frac{1}{11}\)

\(\frac{2.3.4}{2.3.4.5}=\frac{6.4}{6.4.5}=\frac{24}{24.5}=\frac{1}{5}\)

cộng các phấn số cùng mẫu trước

\(\frac{12}{25}+\frac{3}{5}+\frac{13}{25}=\left(\frac{12}{25}+\frac{13}{25}\right)+\frac{3}{5}=1+\frac{3}{5}=\frac{8}{5}\)

\(\frac{3}{2}+\frac{2}{3}+\frac{4}{3}=\left(\frac{2}{3}+\frac{4}{3}\right)+\frac{3}{2}=2+\frac{3}{2}=\frac{7}{2}\)

\(\frac{3}{5}+\frac{7}{5}+\frac{3}{4}=\left(\frac{3}{5}+\frac{7}{5}\right)+\frac{3}{4}=2+\frac{3}{4}=\frac{11}{4}\)

a)=7/8

b)=2/3

c)=11/24

\(a,\frac{4}{5}\times\frac{a}{b}=\frac{7}{10}\)

               \(\frac{a}{b}=\frac{7}{10}:\frac{4}{5}\)

               \(\frac{a}{b}=\frac{7}{10}\times\frac{5}{4}\)

                \(\frac{a}{b}=\frac{7}{8}\)

\(b,\frac{1}{3}:\frac{a}{b}=\frac{2}{3}:\frac{4}{3}\)

    \(\frac{1}{3}:\frac{a}{b}=\frac{2}{3}\times\frac{3}{4}\)

     \(\frac{1}{3}:\frac{a}{b}=\frac{1}{2}\)

            \(\frac{a}{b}=\frac{1}{3}:\frac{1}{2}\)

            \(\frac{a}{b}=\frac{1}{3}\times2\)

             \(\frac{a}{b}=2\)

\(c,\frac{a}{b}+\frac{3}{8}=\frac{5}{6}\)

               \(\frac{a}{b}=\frac{5}{6}-\frac{3}{8}\)

                \(\frac{a}{b}=\frac{11}{24}\)

12/5 -4/5 =8/5

11/6 -2/3 =21/18 =7/6

7/8 -2/7 =33/56

4 -8/5 =20/5-8/5 =12/5

2 -3/8 =16/8 -3/8 =13/8

16/7 -2 =16/7 -14/7 =2/7

25/4 -3=25/4 -12/4 =13/4

câu 2 :                                       câu 3 :

a) 8/5                                         a)4 - 8/5 = 20/5 - 8/5 =12/5

b) 7/6                                         b)2 - 3/8 =16/8 - 3/8 = 13/8 

c) 35/56                                      c)16/7 - 2 = 16/7 - 14/7 = 2/7

                                                  d)25/4 - 3 = 25/4 - 12/4 = 13/4

\(3+\frac{2}{5}-\frac{3}{4}\times\frac{4}{5}\)

\(=3+\frac{2}{5}-\frac{3}{4}\)

\(=\frac{3\times20+2\times4-3\times5}{20}\)

\(=\frac{60+8-15}{20}\)

\(=\frac{68-15}{20}\)

\(=\frac{53}{20}\)

\(5-\frac{7}{9}+\frac{2}{3}-\frac{5}{6}:\frac{4}{9}\)

\(=5-\frac{7}{9}+\frac{2}{3}-\frac{45}{24}\)

\(=\frac{5\times72-7\times8+2\times24-45\times3}{72}\)

\(=\frac{360-56+48-135}{72}\)

\(=\frac{217}{72}\)

\(\frac{1}{2}+\frac{2}{3}+\frac{3}{5}=\frac{3}{6}+\frac{4}{6}+\frac{3}{5}\)

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

\(=\frac{35}{30}+\frac{18}{30}=\frac{53}{30}\)

\(\frac{3}{8}+\frac{3}{4}+\frac{1}{16}=\frac{6}{16}+\frac{12}{16}+\frac{1}{16}\)

=\(\frac{18}{16}+\frac{1}{16}\)

\(=\frac{19}{16}\)

a 98+99=197

b khó quá

\(\frac{3}{4}+\frac{2}{3}=\frac{9}{12}+\frac{8}{12}=\frac{17}{12}\)

\(\frac{9}{2}-4=\frac{9}{2}-\frac{8}{2}=\frac{1}{2}\)

\(\frac{4}{5}\times\frac{3}{2}=\frac{4\times3}{5\times2}=\frac{12}{10}=\frac{6}{5}\)

\(\frac{5}{6}:\frac{6}{5}=\frac{5}{6}\times\frac{5}{6}=\frac{25}{36}\)

de vaiiiiiiiiii

làm đi

\(\frac{12}{20}\)= \(\frac{6}{10}\)= \(\frac{3}{5}\)

\(\frac{3}{4}\)= \(\frac{9}{12}\)= \(\frac{12}{16}\)= \(\frac{15}{20}\)

\(\frac{75}{45}\)= \(\frac{15}{9}\)= \(\frac{5}{3}\)

\(\frac{3}{4}\)= \(\frac{18}{24}\)= \(\frac{12}{16}\)

12/20 = 6/10 = 3/5

3/4 = 9/12 = 12/16 = 15/20

75/45 = 15/9 = 5/3

3/4 = 18/24 = 12/16

Tk mk nha