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
 

27/8 - 7/3 + 4/3 - 2

= 27/8 -  (7/3 - 4/3) - 2

= 27/8 - 1 - 2

=27/8 - 3

= 3/8 

= 27/8-(7/3-4/3)-1

=27/8-1-1

=27/8-2

=11/8

- Ủng hộ -

~minhanh~

7/9 - 3/7 + 2/3 - 4/7

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

= 13/9 - 1 

= 4/9

8,12 x 6 + 16,24 x 4 - 4,06 x 8

= 8,12 x 6 + 8,12 x 2 x 4 - 8,12 : 2 x 8

= 8,12 x 6 + 8,12 x 8 - 8,12 x 4 

= 8,12 x ( 6 + 8 - 4 )

= 8,12 x 10  

81,2 

Ủng hộ nhé ! Chúc bạn học giỏi !

          7/9 - 3/7 + 2/3 - 4/7

       = 7/9 + 2/3 - 3/7 - 4/7

       = 7/9 + 2/3 - [ 3/7 + 4/7 ]

       = 13/9 - 1

        = 4/9

           8,12 * 6 + 16,24 * 4 - 4,06 * 8

        = 8,12 * 6 + 8,12 * 2 * 4 - 4,06 * 2 * 4

        = 8,12 * 6 + 8,12 * 8 - 8,12 * 4

        = 8,12 * [ 6 + 8 - 4 ]

        = 8,12 * 10

        = 81,2

                   CHÚC CÁC BẠN THÀNH CÔNG . Nhớ k cho mình nhiều nhiều nhé !

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a \(\frac{4}{18}+\frac{5}{13}+\frac{7}{9}+\frac{21}{13}\)

= \(\left(\frac{4}{18}+\frac{7}{9}\right)+\left(\frac{5}{13}+\frac{21}{13}\right)\)

= \(1+2\)

= \(3\)

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

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

= \(\frac{2}{3}-1\)

= \(-\frac{1}{3}\)

 \(=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+...+\frac{1}{10}\)có 9 p/số

\(=\frac{1}{10}.9=\frac{9}{10}\)

= 1/10 + 1/10 + ...................... + 1/10 có 9 phân số

= 1/10 x 9

= 9/10

ai tk mình mình đang bị âm điểm

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

= \(x^8.\frac{1}{10}.\frac{2}{9}.\frac{3}{8}.\frac{4}{7}.\frac{5}{6}.\frac{6}{5}.\frac{7}{4}.\frac{8}{3}.\frac{9}{2}\)

= \(x^8.\frac{1}{10}.\left(\frac{2}{9}.\frac{9}{2}\right).\left(\frac{3}{8}.\frac{8}{3}\right).\left(\frac{4}{7}.\frac{7}{4}\right).\left(\frac{5}{6}.\frac{6}{5}\right)\)

= \(x^8.\frac{1}{10}.1.1.1.1\)

= \(x^8.\frac{1}{10}\)

Mk ko pik co dung ko nua

=4/10