\(\left(\frac{3}{4}+\frac{2}{11}-\frac{8}{13}\right)+\left(\frac{1}{4}-\frac{5}{13}\right)\)

\(=\frac{3}{4}+\frac{2}{11}-\frac{8}{13}+\frac{1}{4}-\frac{5}{13}\)

\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\frac{2}{11}-\left(\frac{8}{13}+\frac{5}{13}\right)\)

\(=1+\frac{2}{11}-1\)

\(=\frac{2}{11}\)

\(\left(\frac{9}{53}+\frac{21}{31}\right)+\left(\frac{44}{53}-\frac{16}{7}\right)+\frac{10}{31}\)

\(=\frac{9}{53}+\frac{21}{31}+\frac{44}{53}-\frac{16}{7}+\frac{10}{31}\)

\(=\left(\frac{9}{53}+\frac{44}{53}\right)+\left(\frac{21}{31}+\frac{10}{31}\right)-\frac{16}{7}\)

\(=1+1-\frac{16}{7}\)

\(=2-\frac{16}{7}\)

\(=\frac{14}{7}-\frac{16}{7}\)

\(=\frac{-2}{7}\)

\(A=\frac{21}{31}+\frac{-16}{7}+\frac{44}{53}+\frac{10}{21}+\frac{9}{53} \)

\(A=\left(\frac{16}{7}+\frac{10}{21}\right)+\left(\frac{44}{53}+\frac{9}{53}\right)+\frac{21}{31}\)

\(A=\frac{58}{21}+1+\frac{21}{31}\)

\(A=\frac{100}{21}\)

\(B=6\left(\frac{1}{15.18}+\frac{1}{18.21}+...+\frac{1}{87.90}\right)\)

\(B=6\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+...+\frac{1}{87}-\frac{1}{90}\right)\)

\(B=6\left(\frac{1}{15}-\frac{1}{90}\right)\)

\(B=6.\frac{1}{18}\)

\(B=\frac{1}{3}\)

\(\left(\frac{21}{31}+\frac{2013}{6039}\right)-\left(\frac{44}{53}-\frac{10}{31}\right)-\frac{9}{53}\)

\(=\frac{21}{31}+\frac{1}{3}-\frac{44}{53}+\frac{10}{31}-\frac{9}{53}\)

\(=\left(\frac{21}{31}+\frac{10}{31}\right)+\left(\frac{-44}{53}-\frac{9}{53}\right)+\frac{1}{3}\)

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

\(=\frac{1}{3}\)

\(\left(\dfrac{21}{31}+\dfrac{-16}{7}\right)+\left(\dfrac{44}{53}+\dfrac{10}{31}\right)+\dfrac{9}{53}.\)

\(\dfrac{21}{31}-\dfrac{16}{7}+\dfrac{44}{53}+\dfrac{10}{31}+\dfrac{9}{53}=\left(\dfrac{21}{31}+\dfrac{10}{31}\right)+\left(\dfrac{44}{53}+\dfrac{9}{53}\right)-\dfrac{16}{7}=1+1-\dfrac{16}{7}=\dfrac{-2}{7}.\)

Câu a:

(1/4 + -5/13) + (2/11 + -8/13 + 3/4)

= 1/4 - 5/13 + 2/11 - 8/13 + 3/4

= (1/4 + 3/4) - (5/13+ 8/13) + 2/11

= 1 - 1 + 2/11

= 0 + 2/11

= 2/11

Câu b:

(21/31 + -16/7) + (44/53 + 10/31) + 9/53

= 21/31 - 16/7 + 44/53 + 10/31 + 9/53

= (21/31 + 10/31) + (44/53 + 9/53) - 16/7

= 1 + 1 - 16/7

= 2 - 16/7

= -2/7

Câu a:

(1/4 + -5/13) + (2/11 + -8/13 + 3/4)

= 1/4 - 5/13 + 2/11 - 8/13 + 3/4

= (1/4 + 3/4) - (5/13+ 8/13) + 2/11

= 1 - 1 + 2/11

= 0 + 2/11

= 2/11

Câu b:

Câu b:

(21/31 + -16/7) + (44/53 + 10/31) + 9/53

= 21/31 - 16/7 + 44/53 + 10/31 + 9/53

= (21/31 + 10/31) + (44/53 + 9/53) - 16/7

= 1 + 1 - 16/7

= 2 - 16/7

= -2/7

\(a,(\frac{1}{4}+\frac{-5}{13})+(\frac{2}{11}+\frac{-8}{13}+\frac{3}{4})\)

\(= (\frac{1}{4} + \frac{3}{4}) + (\frac{-5}{13} + \frac{-8}{13}) + \frac{2}{11}\)

\(= \frac{4}{4} + \frac{-13}{13} + \frac{2}{11}\)

\(=1+(-1)+\frac{2}{11}=\frac{2}{11}\)

\(b,(\frac{21}{31}+\frac{-16}{7})+(\frac{44}{53}+\frac{10}{31})+\frac{9}{53}\)

\(= (\frac{21}{31} + \frac{10}{31}) + (\frac{44}{53} + \frac{9}{53}) + \frac{-16}{7}\)

\(=\frac{31}{31}+\frac{53}{53}+\frac{-16}{7}=1+1-\frac{16}{7}\)

\(=2-\frac{16}{7}=\frac{14}{7}-\frac{16}{7}=-\frac27\)

\(c,\frac{-5}{7}+\frac{3}{4}+\frac{-1}{5}+\frac{-2}{7}+\frac{1}{4}\)

\(= (\frac{-5}{7} + \frac{-2}{7}) + (\frac{3}{4} + \frac{1}{4}) + \frac{-1}{5}\)

\(= \frac{-7}{7} + \frac{4}{4} + \frac{-1}{5}\)

\(=-1+1-\frac{1}{5}=0-\frac15=-\frac15\)

\(\frac{-3}{31} + \frac{-6}{17} + \frac{1}{25} + \frac{-28}{31} + \frac{-11}{17} + \frac{-1}{5}\)

\(= (\frac{-3}{31} + \frac{-28}{31}) + (\frac{-6}{17} + \frac{-11}{17}) + \frac{1}{25} + \frac{-1}{5}\)

\(= \frac{-31}{31} + \frac{-17}{17} + \frac{1}{25} - \frac{5}{25}\)

\(= -1 + (-1) + \frac{-4}{25}\)

\(=-2-\frac{4}{25}=-\frac{50}{25}-\frac{4}{25}=-\frac{54}{25}\)

Câu 1:

\(=\dfrac{21}{31}+\dfrac{1}{3}-\dfrac{44}{53}+\dfrac{10}{31}-\dfrac{9}{53}=\dfrac{1}{3}\)

Câu 2:

1: =>1,3x=-1,31

=>130x=-131

=>x=-131/130

2: =>(4,5-2x)=11/14:(-11/7)=-7/14=-1/2=-0,5

=>2x=5

=>x=5/2