Bài 1 :

a) \(\frac{12}{21}-\frac{3}{7}+\left(-\frac{2}{3}\right)=\frac{4}{7}-\frac{3}{7}+\left(-\frac{2}{3}\right)=\frac{1}{7}-\frac{2}{3}=-\frac{11}{21}\)

b) \(\left(-\frac{25}{13}\right)+\left(-\frac{9}{17}\right)+\frac{12}{13}+\left(-\frac{25}{17}\right)\)

\(=\left[\left(-\frac{25}{13}\right)+\frac{12}{13}\right]+\left[\left(-\frac{9}{17}\right)+\left(-\frac{25}{17}\right)\right]\)

\(=-1+\left(-2\right)=-1-2=-3\)

c) \(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}-\frac{5}{9}\cdot\frac{3}{13}=\frac{5}{9}\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)=\frac{5}{9}\cdot1=\frac{5}{9}\)

Bài 2 :

a)  \(\frac{2}{3}x+\frac{5}{7}=\frac{3}{10}\)

=> \(\frac{2}{3}x=\frac{3}{10}-\frac{5}{7}=-\frac{29}{70}\)

=> \(x=\left(-\frac{29}{70}\right):\frac{2}{3}=\left(-\frac{29}{70}\right)\cdot\frac{3}{2}=-\frac{87}{140}\)

b) \(x:\frac{5}{2}-\frac{1}{2}=-\frac{2}{3}\)

=> \(x:\frac{5}{2}=-\frac{2}{3}+\frac{1}{2}=-\frac{1}{6}\)

=> \(x=\left(-\frac{1}{16}\right)\cdot\frac{5}{2}=-\frac{5}{32}\)

c) Bạn chỉ cần xét hai trường hợp âm và dương thôi :>

\(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)

\(=\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)

\(=\frac{5}{9}.\frac{13}{13}=\frac{5}{9}.1=\frac{5}{9}\)

_Vi hạ_

loi nhanh nha

\(a)\dfrac{5}{12}+\dfrac{5}{3}+\dfrac{2}{12}+\dfrac{2}{3}\)

\(=\left(\dfrac{5}{12}+\dfrac{2}{12}\right)+\left(\dfrac{5}{3}+\dfrac{2}{3}\right)\)

\(=\dfrac{7}{12}+\dfrac{7}{3}\)

\(=\dfrac{7}{12}+\dfrac{28}{12}\)

\(=\dfrac{35}{12}\)

\(b)\dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}-\dfrac{5}{9}.\dfrac{3}{13}\)

\(=\dfrac{5}{9}.1.\dfrac{7}{13}+\dfrac{5}{9}-\dfrac{5}{9}.\dfrac{3}{13}\)

\(=\dfrac{5}{9}.\left(1+\dfrac{7}{13}-\dfrac{3}{13}\right)\)

\(=\dfrac{5}{9}.\dfrac{17}{13}\)

\(=\dfrac{85}{117}\)

A=7/19(8/11+3/11)+12/19

=7/19.1+12/19

=1

B=5/9(7/13+9/13-3/13)

=5/9.1

=5/9

ba đội công nhân có tất cả 192 người . số người đội 1 chiếm 1/4 tổng số. số người đội 2 bằng 125% đội 1. tính số người đội 3

tổng của hai số lẻ liên tiếp là 636 . Tìm số bé hơn

Bài 1:

\(\frac{3}{7}\cdot\frac{9}{2}-\frac{1}{14}\cdot\frac{1}{13}\)=\(\frac{27}{14}-\frac{1}{14}\cdot\frac{1}{13}\)

                                          = \(\frac{1}{14}\left(27-\frac{1}{3}\right)\)

                                         = \(\frac{1}{14}\cdot\frac{350}{13}\)=\(\frac{25}{13}\)

bài 2:\(\frac{5}{9}\cdot\frac{7}{13}+\frac{5}{9}\cdot\frac{9}{13}\cdot\frac{3}{13}\)= \(\frac{5}{9}\cdot\frac{1}{13}\left(7+9\cdot\frac{3}{13}\right)\)

                                                            = \(\frac{5}{9}\cdot\frac{1}{13}\cdot\frac{94}{13}\)=\(\frac{470}{1521}\)

có j sai xin mn chỉ bảo!

Câu trả lời là \(\frac{5}{9}\)phải không ?

\(\frac{5}{9}\)

Giải:

a) \(\left(9\dfrac{4}{9}+5\dfrac{2}{3}\right)-5\dfrac{1}{2}\) 

\(=\left(\dfrac{85}{9}+\dfrac{17}{3}\right)-\dfrac{11}{2}\) 

\(=\dfrac{136}{9}-\dfrac{11}{2}\) 

\(=\dfrac{173}{18}\) 

b) \(\dfrac{13}{9}.\dfrac{15}{4}-\dfrac{13}{9}.\dfrac{7}{4}-\dfrac{13}{9}.\dfrac{5}{4}\) 

\(=\dfrac{13}{9}.\left(\dfrac{15}{4}-\dfrac{7}{4}-\dfrac{5}{4}\right)\) 

\(=\dfrac{13}{9}.\dfrac{3}{4}\) 

\(=\dfrac{13}{12}\) 

c) \(\dfrac{2}{3}+\dfrac{5}{8}-\dfrac{-1}{3}+0,375\) 

\(=\left(\dfrac{2}{3}-\dfrac{-1}{3}\right)+\left(\dfrac{5}{8}+\dfrac{3}{8}\right)\) 

\(=1+1\) 

\(=2\)

d) \(75\%-3\dfrac{1}{2}+1,5:\dfrac{10}{7}\) 

\(=\dfrac{3}{4}+\dfrac{7}{2}+\dfrac{3}{2}:\dfrac{10}{7}\) 

\(=\dfrac{3}{4}+\dfrac{7}{2}+\dfrac{21}{20}\) 

\(=\dfrac{53}{10}\) 

e) \(1\dfrac{13}{15}.\left(0,5\right)^2.3+\left(\dfrac{8}{15}-1\dfrac{19}{60}\right):1\dfrac{23}{24}\) 

\(=\dfrac{28}{15}.\dfrac{1}{4}.3+\left(\dfrac{8}{15}-\dfrac{79}{60}\right):\dfrac{47}{24}\) 

\(=\dfrac{7}{5}+\dfrac{-47}{60}:\dfrac{47}{24}\) 

\(=\dfrac{7}{5}+\dfrac{-2}{5}\) 

\(=1\)

a: \(=\dfrac{5}{9}\cdot\dfrac{7}{4}+\dfrac{13}{9}\cdot\dfrac{7}{4}=\dfrac{7}{4}\cdot2=\dfrac{7}{2}\)

b: \(=\dfrac{14}{13}\cdot2+\dfrac{3}{13}\cdot2-2\cdot\dfrac{7}{13}=\dfrac{28}{13}+\dfrac{6}{13}-\dfrac{14}{13}=\dfrac{20}{13}\)