( 8/14 + 6/14 ) + ( 5/12 - 1/12 + 8/12 )

= 1 + ( 4/12 + 8/12 )

= 1 + 1 = 2

=(8/14+6/14 )+(5/12+8/12-1/12)

=1+1

=2

324 – 20 + 61 = 304 + 61 = 365

188 + 12 – 50 = 200 - 50 = 120

a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145

b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7

c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11

a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21

b) (5/17 x 21/32 x 47/24 x 0)
= 0

c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7

a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x

b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15

c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2

a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36

câu,b,không,đủ,thông,tin,nhan,bạn.

=28/14+22/11=2+2=4

( 24/14 + 4/14) + (12/11 + 10/11)

=28/14 +22/11

=2+2

=4

\(\frac{24}{14}+\frac{12}{11}+\frac{4}{14}+\frac{10}{11}\)

\(=\frac{24}{14}+\frac{4}{14}+\frac{12}{11}+\frac{10}{11}\)

\(=2+2=4\)

\(\frac{8}{14}+\frac{5}{12}+\frac{6}{14}+\frac{8}{12}-\frac{1}{12}\)

\(=\left(\frac{8}{14}+\frac{6}{14}\right)+\left(\frac{5}{12}+\frac{8}{12}-\frac{1}{12}\right)\)

\(=1+1\)

\(=2\)

\(\frac{8}{14}+\frac{5}{12}+\frac{6}{14}+\frac{8}{12}-\frac{1}{12}\)

\(=\)\(\left(\frac{8}{14}+\frac{6}{14}\right)+\left(\frac{5}{12}+\frac{8}{12}-\frac{1}{12}\right)\)

\(=\)\(1+1\)

\(=\)\(2\)

\(\frac{8}{14}\) \(+\) \(\frac{5}{12}\) \(+\) \(\frac{6}{14}\) \(+\) \(\frac{8}{12}\) \(-\) \(\frac{1}{12}\)

=   (  \(\frac{8}{14}\) \(+\) \(\frac{6}{14}\))    \(+\)(  \(\frac{5}{12}\) \(+\) \(\frac{8}{12}\) \(-\) \(\frac{1}{12}\))

=               \(1\)                    \(+\)                       \(1\)

=                           \(2\)

- Hok T - 

Câu a :  

\(\dfrac{5}{12}+\dfrac{3}{4}+\dfrac{1}{3}\\ =\dfrac{5}{12}+\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{3}{2}\)

câu b : 

\(\dfrac{1}{4}+\dfrac{3}{7}+\dfrac{11}{14}\\ =\dfrac{7}{28}+\dfrac{12}{28}+\dfrac{22}{28}=\dfrac{41}{28}\)

câu c : 

\(\dfrac{1}{4}+\dfrac{3}{12}+\dfrac{12}{36}\\ =\dfrac{3}{12}+\dfrac{3}{12}+\dfrac{4}{12}\\ =\dfrac{10}{12}=\dfrac{5}{6}\)

Biểu thức đâu bạn ?

mình ko hieu?

Ví dụ biểu thức a+1 với a=12

thì a+1=12+1=13 

đại loại vậy

mk làm lại:

\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{20}\)

=\(\left(\frac{1}{11}-\frac{11}{11}\right)+\left(\frac{1}{12}-\frac{12}{12}\right)+\left(\frac{1}{13}-\frac{13}{13}\right)+...+\left(\frac{1}{20}-\frac{20}{20}\right)\)

=\(\frac{-10}{11}+\frac{-11}{12}+\frac{-12}{13}+...+\frac{-19}{20}\)

=\(\frac{-10}{20}\)

\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{14}\)

=\(\left(\frac{1}{11}-\frac{11}{11}\right)+\left(\frac{1}{12}-\frac{12}{12}\right)+\left(\frac{1}{13}-\frac{13}{13}\right)+...+\left(\frac{1}{14}-\frac{14}{14}\right)\)

=\(\frac{-10}{11}+\frac{-11}{12}+\frac{-12}{13}+...+\frac{-13}{14}\)

=\(\frac{-10}{14}\)

xin lỗi, bài này mình ghi lộn, bài này là 1/11+1/12+1/13+...+1/20