a) \(1678\cdot24+77\cdot1678-1678=1678\left(24+77-1\right)=167800\)

b) Ta có: \(\dfrac{2}{5}+\dfrac{4}{11}+\dfrac{3}{5}+\dfrac{18}{11}+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{4}{11}+\dfrac{18}{11}\right)+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=3+\dfrac{1}{4}+\dfrac{1}{6}\)

\(=\dfrac{36}{12}+\dfrac{3}{12}+\dfrac{2}{12}=\dfrac{41}{12}\)

c) \(\dfrac{7}{9\cdot7}+\dfrac{7}{9\cdot4}-\dfrac{7}{9\cdot10}\)

\(=\dfrac{7}{9}\left(\dfrac{1}{7}+\dfrac{1}{4}-\dfrac{1}{10}\right)\)

\(=\dfrac{7}{9}\cdot\left(\dfrac{20}{140}+\dfrac{35}{140}-\dfrac{14}{140}\right)\)

\(=\dfrac{7}{9}\cdot\dfrac{41}{140}=\dfrac{41}{180}\)

a: \(=\dfrac{3}{5}+\dfrac{2}{7}=\dfrac{21+10}{35}=\dfrac{31}{35}\)

b: \(=\dfrac{6}{5}+\dfrac{3}{2}\cdot\dfrac{1}{3}=\dfrac{6}{5}+\dfrac{1}{2}=\dfrac{12+5}{10}=\dfrac{17}{10}\)

c: \(=\dfrac{5\cdot3}{9}=\dfrac{5}{3}\)

d: =5-2/3*6/5

=5-12/15

=5-4/5

=21/5

\(\dfrac{4}{5}\times\dfrac{16}{9}-\dfrac{7}{9}\times\dfrac{4}{5}-\dfrac{4}{5}\)
\(=\dfrac{4}{5}\times\left(\dfrac{16}{9}-\dfrac{7}{9}-1\right)\)
\(=\dfrac{4}{5}\times0\)
\(=0\)
#Đang Bận Thở

4/5 x 16/9 - 7/9 x 4/5 - 4/5

= 4/5 x ( 16/9 - 7/9 - 1 )

= 4/5 x 0 = 0

=\(\dfrac{4}{5}\times\left(\dfrac{16}{9}-\dfrac{7}{9}-1\right)\)

=\(\dfrac{4}{5}\times0\) = 0

=2/3.9/7.4/15+5/7

=6/7.4/15+5/7

=8/35+5/7

=8/35+25/35

=33/35

\(\dfrac{2}{3}:\dfrac{7}{9}\times\dfrac{4}{15}+\dfrac{5}{7}=\dfrac{6}{7}\times\dfrac{4}{15}+\dfrac{5}{7}=\dfrac{8}{35}+\dfrac{5}{7}=\dfrac{33}{35}\)

2/3:7/9x4/15+5/7

\(=\dfrac{2}{3}\times\dfrac{9}{7}\times\dfrac{4}{15}+\dfrac{5}{7}\)

=\(\dfrac{2.9.4}{3.7.15}+\dfrac{5}{7}\)

\(=\dfrac{8}{35}+\dfrac{5}{7}\)

\(=\dfrac{8}{35}+\dfrac{25}{35}\)

\(=\dfrac{33}{35}\)

9x1=9

9x2=18

9x3=27

9x4=36

9x5=45

ai k mk mk sẽ k lại @!@#$@ ủng hộ nha ^_^

mk 1 cái nhe xin đấy các bn hãy nhấn 

9x1=9

9x2=18

9x3=27

9x4=36

9x5=45

9×1=9

9×2=18

9×3=27

9×4=36

9×5=45

Ủng hộ mk nha ♡_♡^_-

1+2+3+4+5+6+7+8+9X4-2+15=85

9x6=54

9x5=45

9x4=36

9x3=27

9x2=18

9x1=9

k mình nhé chúc năm mới vui vẻ ^.^

9x6=54

9x5=45

9x4=36

9x3=27

9x2=18

9x6=54

9x5=45

9x4=36

9x3=27

9x2=18

Số cần tìm là:

1+2+3+4+5+6+7+8+9x4:2+99+1=163

Đs:163

đung 100%

Tổng Trên là : 154

1+2+3+4+5+6+7+8+9x4:2+99+1

=1+2+3+4+5+6+7+8+36:2+99+1

=1+2+3+4+5+6+7+8+18+99+1

=154

\(\frac{7}{9}\times\frac{3}{5}+\frac{3}{5}\times\frac{5}{6}+\frac{3}{5}\times1\)

\(=\frac{3}{5}\times\left(\frac{7}{9}+\frac{5}{6}+1\right)\)

\(=\frac{3}{5}\times\frac{47}{18}\)

\(=\frac{47}{30}\)

 #hoktot<3#