\(12\frac{4}{5}\)=\(\frac{64}{5}\).

Ta có :

\(\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)

\(12\frac{4}{5}+\frac{4}{5}=\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)

\(12\frac{4}{5}+\frac{4}{5}=\frac{12x5+4}{5}+\frac{4}{5}=\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)

13/4+23/6-4/2=39/12+46/12-24/12 

                    =85/12-24/12

                    =61/12

chúc bạn học giỏi

\(\frac{12}{5}+\frac{23}{4}=\frac{48}{20}+\frac{115}{20}=\frac{163}{20}\)

\(=\frac{163}{20}\)

\(\frac{12}{5}+\frac{23}{4}\) 

\(=\frac{24}{20}+\frac{115}{20}\) 

\(=\frac{139}{20}\) 

1/3+1/4+4/5-1/2=4/12+3/12+4/5-1/2=7/12+4/5-1/2=35/60+48/60-1/2=83/60-1/2=83/60-30/60

=53/60

MTC;60

20/60+15/60+12/60-30/60

=20+15+12-30

=17    nha bn

MẪU SỐ CHUNG NHỎ NHẤT LÀ 60

\(\frac{20}{60}+\frac{15}{60}+\frac{12}{60}-\frac{30}{60}=\frac{20+15+12-30}{60}=\frac{17}{60}\)

\(2\frac{4}{3}+\frac{4}{12}=\frac{2.3+4}{3}+\frac{4}{12}=\frac{10}{3}+\frac{4}{12}=\frac{40}{12}+\frac{4}{12}=\frac{44}{12}=\frac{11}{3}\)

\(2\frac{4}{3}=\frac{10}{3}\)

\(\frac{10}{3}+\frac{4}{12}=\frac{120}{36}+\frac{12}{36}\)

\(=\frac{132}{36}=\frac{22}{6}=\frac{11}{3}\)

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{3+6-2}{12}\)

\(=\frac{7}{12}\)

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{9}{12}-\frac{2}{12}\)

\(=\frac{7}{12}\)

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{7}{12}\)

\(-\frac{3}{4}< \frac{4}{45}\)

Vì : \(-\frac{3}{4}< 1\)

       \(\frac{4}{45}>1\)

\(\Rightarrow-\frac{3}{4}< \frac{4}{45}\)

\(\frac{-3}{4}....\frac{4}{45}\)

\(=\frac{-135}{180}....\frac{20}{180}\)

Ta có : - 135 < 20 

Nên => \(\frac{-135}{180}< \frac{20}{180}\)

KL : \(\frac{-3}{4}< \frac{4}{45}\)

Cách 2 : So sánh tử với tử , mẫu với mẫu

Ta thấy : - 3 < 4

              4 < 45

=> \(\frac{-3}{4}< \frac{4}{45}\)

\(-3,2\left(3\right)\)

\(\left(-\frac{4}{3}\right)+\left(-\frac{2}{5}\right)+\left(-\frac{3}{2}\right)\)
\(=-\frac{26}{15}+\left(-\frac{3}{2}\right)\)
\(=-3,2333....\)

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

= 5/2 x 4/3

=\(\frac{20}{6}\)

M.n tk giùm em vs ạ !! ^_^