`(12/26+5/8)+7/13`

`=(6/13+5/8)+7/13`

`=(6/13+7/13)+5/8`

`=1+5/8=13/8`

`(12/26 +5/8) +7/13 `

`= 6/13 + 5/8 + 7/13`

`= (6/13 + 7/13) + 5/8`

`= 13/13 + 5/8`

`= 1 + 5/8 `

`= 8/8 + 5/8 `

`= 13/8`

(12/26+5/8)+7/13

=(12/26+7/13)+5/8

=1+5/8=8/8+5/8=13/8

6/13 + 5/8 + 7/13

= 6/13 + 7/13 + 5/8

= 1 + 5/8 = 1/5/8 

(12/26+5/8)+7/13

1+5/8 =13/8

Ai ủng hộ cho cái Li-Ke đi mà

a. bằng77

b. bằng 13

lớp 2 đã học cái này rồi à

a. bằng77

b. bằng 13

( 12/26 + 5/8 )  + 7/13

= 12/26 + 5/8 + 7/13

= 5/8 + 12/26 + 7/13

= 5/8 + 12/26 + 14/26

= 5/8 + 1

= 13/8

( \(\frac{12}{26}+\frac{5}{8}\) )+\(\frac{7}{13}\)

= \(\frac{6}{13}+\frac{5}{8}\)+\(\frac{7}{13}\)

=( \(\frac{6}{13}+\frac{7}{13}\))+ \(\frac{5}{8}\)

=1+\(\frac{5}{8}\)

=\(1\frac{5}{8}=\frac{13}{8}\)

Chỉnh lại :

( 12/26 + 7/13 ) + 5/8 = 1 + 5/8 = 13/8

\(\dfrac{12}{7}\times\dfrac{4}{13}+\dfrac{12}{14}\times\dfrac{14}{26}-\dfrac{6}{7}\times\dfrac{2}{13}\)

= \(\dfrac{6}{7}\times\dfrac{4\times2}{13}+\dfrac{6}{7}\times\dfrac{7}{13}-\dfrac{6}{7}\times\dfrac{2}{13}\)

= \(\dfrac{6}{7}\times\left(\dfrac{8}{13}+\dfrac{7}{13}-\dfrac{2}{13}\right)\)

= \(\dfrac{6}{7}\times1\) = \(\dfrac{6}{7}\)

=6/13+7/13+5/8=1+5/8=13/8

\(\dfrac{12}{13}+\dfrac{2}{7}+\dfrac{8}{13}+\dfrac{6}{13}+\dfrac{5}{7}\)
\(=\left(\dfrac{12}{13}+\dfrac{8}{13}+\dfrac{6}{13}\right)+\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\)
\(=2+1\)
\(=3\)

= ( 12/13 + 8/13 + 6/13 ) + ( 2/7 + 5/7 )

= 26/13 + 7/7

= 2 + 1

= 3

cảm ơn bạn đã giải 3 bài giúp mình!

\(1+2+3+4+5+...+28+29=\left(1+29\right).29:2=435\)

(1+29)+(2+28)+(3+27)+(4+26)+(5+25)+(6+24)+(7+23)+(8+22)+(9+21)+(10+20)+(11+19)+(12+18)+(13+17)+(14+16)+15

=30+30+30+30+30+30+30+30+30+30+30+30+30+30+15

=30x14+15

=435

435

bạn lấy số đầu cộng số cuối được bao nhiêu cộng với 15

Bạn tính theo từng phần nha