c)=13,8+(7+4,25)-5,25

=13,8+(11.25-5.25)

=13,8+6=19,8

b, = 7/9 - 2/3 - < 4/7 =3/7 > 

= 13/9 - 1

= 4/9

giúp mình với

\(a,\dfrac{7}{9}-\dfrac{2}{7}+\dfrac{2}{3}+\dfrac{4}{7}\\ =\left(\dfrac{7}{9}+\dfrac{6}{9}\right)+\left(\dfrac{4}{7}-\dfrac{2}{7}\right)\\ =\dfrac{13}{9}+\dfrac{2}{7}\\ =\dfrac{109}{63}\\ b,13,8+7-5,25+4,25\\ =\left(13,8+7\right)-\left(5,25-4,25\right)\\ =20,8-1\\ =19,8\)

a \(\left(\dfrac{4}{7}-\dfrac{2}{7}\right)+\left(\dfrac{7}{9}+\dfrac{2}{3}\right)=\dfrac{2}{7}+\left(\dfrac{7}{9}+\dfrac{6}{9}\right)=\dfrac{2}{7}+\dfrac{15}{9}=\dfrac{2}{7}+\dfrac{5}{3}=\dfrac{6}{21}+\dfrac{35}{21}=\dfrac{41}{21}\)

b \(20.8-1=19.8\)

a)\(\frac{7}{9}-\frac{3}{7}+\frac{2}{3}-\frac{4}{7}\)

\(=\frac{7}{9}+\frac{-3}{7}+\frac{2}{3}+\frac{-4}{7}\)

\(=\left(\frac{7}{9}+\frac{2}{3}\right)+\left(\frac{-3}{7}+\frac{-4}{7}\right)\)

\(=\frac{13}{9}-1\)

\(=\frac{4}{9}\)

b)13,8 + 7 - 5,25 + 4,25

=(13,8 + 7 + 4,25 ) - 5,25

=25,05 - 5,25

=19,8

a/ = (7/9+2/3)-(3/7+4/7)

    =1-1=0
 

a) 7/9 - 3/7 + 2/3 - 4/7

= 7/9 - 3/7 + 6/9 - 4/7

=( 7/9 - 6/9 ) + ( 3/7 + 4/7 )

= 1/9 + 1

=10/9

b) 13,8 + 7 - 5,25 + 4,25

=(13,8 + 7 ) - (5,25 + 4,25 )

=20,8 - 9,5

= 11,3

a) \(\dfrac{5}{9}+\dfrac{13}{7}+\dfrac{15}{13}+\dfrac{8}{7}+\dfrac{4}{9}+\dfrac{11}{13}\)

\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{13}{7}+\dfrac{8}{7}\right)+\left(\dfrac{15}{13}+\dfrac{11}{13}\right)\)

\(=1+3+2\)

\(=6\)

b) \(\dfrac{3}{5}+\dfrac{18}{9}+\dfrac{4}{10}\)

\(=0,6+2+0,4\)

\(=\left(0,6+0,4\right)+2\)

\(=1+2\)

\(=3\)

\(a\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{13}{7}+\dfrac{8}{7}+\dfrac{15}{13}+\dfrac{11}{13}=\dfrac{9}{9}+\dfrac{21}{7}+\dfrac{26}{13}=1+3+2=6\)

\(b\dfrac{3}{5}+2+\dfrac{2}{5}=\dfrac{5}{5}+2=1+2=3\)

a) \(\dfrac{5}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{5}{7}\)

\(=\dfrac{5}{7}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=\dfrac{5}{7}\times1\)

\(=\dfrac{5}{7}\)

b) \(\dfrac{1}{10}+\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{9}{10}-1\)

\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{1}{10}+\dfrac{9}{10}-1\right)\)

\(=1+0\)

\(=1\)

c) \(\dfrac{5}{7}\times\dfrac{5}{9}+\dfrac{4}{9}\times\dfrac{5}{7}+\dfrac{2}{7}\)

\(=\dfrac{5}{7}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\dfrac{2}{7}\)

\(=\dfrac{5}{7}+\dfrac{2}{7}\)

\(=1\)

d) \(\dfrac{2}{7}+\dfrac{2}{8}+\dfrac{1}{4}+\dfrac{1}{7}+\dfrac{4}{7}\)

\(=\left(\dfrac{2}{8}+\dfrac{1}{4}\right)+\left(\dfrac{2}{7}+\dfrac{1}{7}+\dfrac{4}{7}\right)\)

\(=\left(\dfrac{1}{4}+\dfrac{1}{4}\right)+1\)

\(=\dfrac{1}{2}+1\)

\(=\dfrac{3}{2}\)

e) \(\dfrac{4}{5}+\dfrac{3}{10}+\dfrac{2}{10}+0,7\)

\(=\dfrac{4}{5}+\dfrac{5}{10}+\dfrac{7}{10}\)

\(=\dfrac{4}{5}+\dfrac{12}{10}\)

\(=\dfrac{4}{5}+\dfrac{6}{5}\)

\(=\dfrac{10}{5}\)

\(=2\)

g) \(362\times728+326\times272\)

\(=326\times\left(728+272\right)\)

\(=326\times1000\)

\(=326000\) 

a: \(=\left(15-6-\dfrac{13}{18}\right):\dfrac{298}{27}-\dfrac{17}{8}:\dfrac{51}{40}\)

\(=\dfrac{149}{18}\cdot\dfrac{27}{298}-\dfrac{5}{3}=\dfrac{3}{2}-\dfrac{5}{3}=\dfrac{9-10}{6}=\dfrac{-1}{6}\)

b: \(=\dfrac{-16}{5}\cdot\dfrac{-15}{64}+\dfrac{-22}{15}:\dfrac{11}{2}\)

\(=\dfrac{3}{4}-\dfrac{4}{15}=\dfrac{29}{60}\)

c: \(=\dfrac{-7}{9}\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+5+\dfrac{7}{9}=\dfrac{-7}{9}+\dfrac{7}{9}+5=5\)

d: \(=\dfrac{1}{2}\cdot\dfrac{4}{3}\cdot10\cdot\dfrac{1}{5}\cdot\dfrac{3}{4}=1\)

e: \(=\dfrac{4}{25}+\dfrac{11}{2}\cdot\dfrac{5}{2}+\dfrac{-23}{4}=\dfrac{204}{25}\)