a) \(\dfrac{25}{37}\times\dfrac{18}{29}+\dfrac{18}{29}\times\dfrac{12}{37}\)

\(=\dfrac{18}{29}\times\left(\dfrac{25}{37}+\dfrac{12}{37}\right)\)

\(=\dfrac{18}{29}\times\dfrac{37}{37}\)

\(=\dfrac{18}{29}\times1\)

\(=\dfrac{18}{29}\)

b) \(\dfrac{31}{85}\times\dfrac{11}{19}+\dfrac{31}{85}\times\dfrac{12}{19}-\dfrac{42}{19}\times\dfrac{31}{85}\)

\(=\dfrac{31}{85}\times\left(\dfrac{11}{19}+\dfrac{12}{19}-\dfrac{42}{19}\right)\)

\(=\dfrac{31}{85}\times\dfrac{-19}{19}\)

\(=\dfrac{31}{85}\times-1\)

\(=-\dfrac{31}{85}\)

c) \(\dfrac{16}{53}:\dfrac{17}{9}-\dfrac{16}{53}:\dfrac{17}{8}\)

\(=\dfrac{16}{53}:\left(\dfrac{9}{17}-\dfrac{8}{17}\right)\)

\(=\dfrac{16}{53}:\dfrac{1}{17}\)

\(=\dfrac{16}{901}\)

c) \(\dfrac{1}{5}\times\dfrac{12}{31}\times\dfrac{4}{3}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\dfrac{12}{31}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\left(\dfrac{12}{31}+\dfrac{19}{31}\right)\)

\(=\dfrac{4}{15}\times\dfrac{31}{31}\)

\(=\dfrac{4}{15}\times1\)

\(=\dfrac{4}{15}\)

a: =18/29*(25/37+12/37)

=18/29

b: =31/85(11/19+12/19-42/19)

=-31/85

c; =16/53(9/17+8/17)=16/53

d: =4/15(12/31+19/31)=4/15

a) 15 x 141 + 59 x 15

= 15.(141 + 59) 

= 15.200

= 3000

b) 17 x 85 + 15 x 17 - 120

= 17(85 + 15) - 120 

= 17.100 - 120

= 1700 - 120

= 1580

15*(141+59)

=15*200

=3000

17*(85+150)-120

=17*100-120

=1700-120

=1580

a)15.141+ 59.15

=15.(141+ 59)

=15.200

= 3000

b)17.85+ 15.17- 120

=17.(85+ 15)   - 120

=17.  100        - 120

=    1700         - 120

=            1580

\(\Leftrightarrow\dfrac{x+100}{86}+\dfrac{x+100}{85}+\dfrac{x+100}{84}+\dfrac{x+100}{83}=0\)

=>x+100=0

hay x=-100

hacker mà ko làm dc bài này ha?? :))

(9+13+17+...+85)-(x+x+x+...+x) = 925

=> 760 - 20x = 925

20x = 925 + 760

20x = 1685

x = 1685 : 20

x = 84,25

Trình bày chi tiết ra được không?

a) 27 x (-17) + 17 x 127

= 27 x (-17) - 17 x (-127)

= -17 x (27-127)

= -17 x -100 = 1700

b) 2 x (1 +32) - 2 x 32

= 2 x (1 + 32 - 32)

= 2 x 1 = 2

\(25+17+75+32-85+36=100\)

K mình nha mình sẽ là người đầu tiên k bạn! Mình ko nhắn tin được thông cảm ! Nhớ k

25 + 17 + 75 + 32 - 85 + 36 = 270

25+17+75+32-85+36= 100

\(\dfrac{x+11}{89}+\dfrac{x+13}{87}=\dfrac{x+15}{85}+\dfrac{x+17}{83}\\\Leftrightarrow\left(\dfrac{x+11}{89}+1\right)+\left(\dfrac{x+13}{87}+1\right)=\left(\dfrac{x+15}{85}+1\right)+\left(\dfrac{x+17}{83}+1\right)\\ \Leftrightarrow\dfrac{x+100}{89}+\dfrac{x+100}{87}-\dfrac{x+100}{85}-\dfrac{x+100}{83}=0\\ \Leftrightarrow\left(x+100\right)\left(\dfrac{1}{89}+\dfrac{1}{87}-\dfrac{1}{85}-\dfrac{1}{83}\right)=0\\ \Leftrightarrow x+100=0\left(vì\dfrac{1}{89}+\dfrac{1}{87}-\dfrac{1}{85}-\dfrac{1}{83}\ne0\right)\\ \Leftrightarrow x=-100\)

  a. 8 và 32                                                  b. 17 và 85

      8 : 32 = 0,25 = 25%                                   17 : 85 = 0,2 = 20%

ta có: (x-7)=85/17

x-7=5

=>x=7+5=12

85 : (x-7) =17

=>x-7 =5

=>x=12

85:(x-7)=17

x-7=85:17

x-7= 5

x=5+7

x=12

học vui~!~!