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

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

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

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

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

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

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

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

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

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

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

\(12\frac{3}{7}\%+12\frac{5}{7}\%=\frac{176}{7}\%\)

\(12\frac{4}{3}+\frac{2}{6}=\frac{41}{3}\)

\(12\frac{4}{3}+\frac{2}{6}=16+\frac{1}{3}=\frac{49}{3}\)

12 + 4/3 + 2/6 = 12 + 5/3 = 41/3

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

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

=> \(\frac{-3}{4}< \frac{4}{45}\)

\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{110}\)

\(=\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{10\cdot11}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\)

\(=\frac{1}{2}-\frac{1}{11}=\frac{9}{22}\)

= 1/2.3 +1/3.4+1/4.5+...+1/10.11

=1/2-1/3+1/3-1/4+1/4-1/5+...+1/10-1/11

=1/2-1/11

=9/22

~~~~~~~~~~~~ chúc bạn học thật giỏi~~~~~~~~~~~~~

Đặt A=1/6 + 1/12 + 1/20 +.........+1/110

A= 1/2x3 +1/3x4 +1/4x5 +......+ 1/10x11

A= 1/2-1/3 +1/3-1/4 +...........+ 1/10-1/11

A=(1/2-1/11) + (1/3 - 1/3) +.......+ (1/10 - 1/10)

A=11/22 -2/22 + 0 +...........+ 0

A=9/22

Vậy A= 9/22

12 : \(\frac{6}{2}=\frac{12}{1}x\frac{6}{2}=\frac{72}{2}\)

đúng không nè bạn

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

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

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

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

\(\frac{25}{2}\%+x=\frac{100}{3}\%\)

                    \(x=\frac{100}{3}\%-\frac{25}{2}\%\)

                    \(x=\frac{200}{6}\%-\frac{75}{6}\%\)

                     \(x=\frac{125}{6}\%\)

= 125 / 6