\(a,x+\dfrac{4}{5}=\dfrac{45}{5}-\left(\dfrac{3}{7}+\dfrac{3}{5}\right)\)

\(x+\dfrac{4}{5}=9-\dfrac{3}{7}-\dfrac{3}{5}\)

\(x+\dfrac{4}{9}=\dfrac{279}{35}\)

\(x=\dfrac{279}{35}-\dfrac{4}{9}\)

\(x=\dfrac{251}{35}\)

\(b,\dfrac{5}{7}+\dfrac{x}{35}=\dfrac{4}{5}\)

\(\dfrac{5}{7}+\dfrac{x}{35}-\dfrac{4}{5}=0\)

\(\dfrac{25}{35}+\dfrac{x}{35}-\dfrac{28}{35}=0\)

\(25+x-28=0\)

\(x=3\)

\(x+\frac{4}{5}=\frac{45}{5}-\left(\frac{3}{7}+\frac{3}{5}\right)\)

\(x+\frac{4}{5}=9-\frac{36}{35}\)

\(x+\frac{4}{5}=\frac{279}{35}\)

\(\Rightarrow x=\frac{251}{35}\)

\(x+\frac{4}{5}=\frac{45}{5}-\left(\frac{3}{7}+\frac{3}{5}\right)\)

\(\Leftrightarrow x+\frac{4}{5}=9-\left(\frac{3}{7}+\frac{3}{5}\right)\)

\(\Leftrightarrow x+\frac{4}{5}=9-\frac{3}{7}-\frac{3}{5}\)

\(\Leftrightarrow x+\frac{4}{5}=\frac{315}{35}-\frac{15}{35}-\frac{21}{35}\)

\(\Leftrightarrow x+\frac{4}{5}=\frac{279}{35}\)

\(\Leftrightarrow x=\frac{279}{35}-\frac{4}{5}\)

\(\Leftrightarrow x=\frac{251}{35}\)

\(\frac{5}{7}+\frac{x}{35}=\frac{4}{5}\)

\(\Leftrightarrow\frac{25}{35}+\frac{x}{35}=\frac{28}{35}\)

\(\Leftrightarrow25+x=28\)

\(\Leftrightarrow x=28-25\)

\(\Leftrightarrow x=3\)

hazz

\(x+\dfrac{4}{5}=\dfrac{45}{5}-\left(\dfrac{3}{7}+\dfrac{3}{5}\right)\\ \Rightarrow x+\dfrac{4}{5}=9-\dfrac{36}{35}\\ \Rightarrow x+\dfrac{4}{5}=\dfrac{279}{35}\\ \Rightarrow x=\dfrac{279}{35}-\dfrac{4}{5}\\ \Rightarrow x=\dfrac{251}{35}\\ \dfrac{5}{7}+\dfrac{x}{35}=\dfrac{4}{5}\\ \Rightarrow\dfrac{x}{35}=\dfrac{4}{5}-\dfrac{5}{7}\\ \Rightarrow\dfrac{x}{35}=\dfrac{3}{35}\\ \Rightarrow x=3\)

a) 2/5+9/5=11/5

b) 15/45+25/30=7/6

c) 28/32+45/72=3/2

d) 8/28+5/30=19/42

bài 2

a) x - 4/5 =4/5 + (3/7+3/5)

x-4/5=4/5+36/35

x-4/5=64/35

x=64/35+4/5

x=92/35

b) x-7/35=4/5

x=4/5+7/35

x=1

nhớ tk m nhé

a = 18/5

b = 3/9 + 5/6 = 6/18 + 25/18  = 31/18

c = 7/8 + 5/8 = 12/8

d = 4/14 + 1/6 = 14/42 + 7/42 = 21/42 -= 7/14

b2

x - 4/5 = 4.5 + ( 3/7 + 3/5 )

x - 4/5 = 49/35

           x = 49/35 + 4/5

              x = 77/35

x - 7/35 = 4/5

             x = 4/5 + 7/35

                 x = 1

mình ko chắc chắn đâu

mình nghĩ mình làm sai

xin lỗi làm nhầm

9 x 5 = 45

63 : 7 = 9

8 x 8 = 64

5 x 7 = 35

8 x 7 =56

3 x 8 = 24

40 : 5 = 8

5 x 5 = 25

7 x 5 = 35

7 x 8 =56

6 x 4 = 24

45 : 9 = 5

7 x 7 = 49

35 : 5 = 7

56 : 8 = 7

2 x 8 = 16

81 : 9 = 9

9 x 9 = 81

35 : 7 = 5

56 : 7 = 8

ay bạn ơi dễ vậy mà

a, ta thấy cả hai vế đều có 4/5 mà lại bằng nhau nên x bằng số hạng còn lại ở vế phải 

x=3/7+3/5

x=36/35

b,x là số hạng chưa biết nên

x=4/5-5/7

x=3/35

cảm ơn Kiều Ngọc Lan tớ đứng đầu olm lớp 4 đấy

a) \(\frac{18}{45}-\frac{4}{12}-\frac{6}{9}-\frac{21}{35}=\frac{2}{5}-\frac{1}{3}-\frac{2}{3}-\frac{3}{5}\)

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

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

\(=\frac{-4}{3}\)

b) \(\frac{4}{3}+\frac{3}{5}+\frac{7}{3}+\frac{2}{5}+\frac{1}{3}=\left(\frac{4}{3}+\frac{7}{3}+\frac{1}{3}\right)+\left(\frac{3}{5}+\frac{2}{5}\right)\)

\(=4+1=5\)

c) \(\frac{1}{3}.\frac{4}{5}.\frac{1}{3}.\frac{6}{5}=\frac{8}{75}\)

d) \(\frac{6}{7}.\frac{8}{13}+\frac{6}{7}.\frac{9}{13}-\frac{3}{13}.\frac{6}{7}\)

\(=\frac{6}{7}.\left(\frac{8}{13}+\frac{9}{13}-\frac{3}{13}\right)\)

\(=\frac{6}{7}.\frac{14}{13}\)

\(=\frac{12}{13}\)