3/7.5/6+4/7.5/6

= 5/6.(3/7+4/7)

=5/6.1

=5/6

3/7*5/6+4/7*5/6

=5/6*(3/7+4/7)

=5/6*1

=5/6

3/7*5/6+4/7*5/6

= 5/6*(3/7+4/7)

=5/6*1

=5/6

a/ = 7,8 x ( 34,5 + 15,5 ) = ..... tự tính 

b/ 11/5 x (3/7 +4/7 )= .......tự tính 

mk nhé

a, 7,8 x 34,5 +15,5 x 7,8 = 7,8 x ( 34,5 + 15,5) =7,8 x 50 =390

b, 3/7 x 11/5 +4/7 x 11/5 = 11/5 x ( 3/7 +4/7) = 11/5 x1=11/5 

=.= hok tốt!!

7,8 .  (34,5 + 15,5 ) 

= 7,8 .50.0

=39,000

7/9 x 5/16 : 5/9 x4/7

=7/9 x 5/16 x9/5 x 4/7

=7/9 x 45/80 x 4/7 

=7/9 x 9/16 x 4/7

=7 x 9 x 4 /9 x 16 x 7

=1/4

a) 3/5x7/9+11/9x3/5

=3/5 x(7/9+11/9)

= 3/5x2

=6/5

b)14/13:1/2+3/13x2-2x7/13

= 14/13 x 2 +3/13 x2 - 2x7/13

=2 x (14/13 +3/13 -7/13)

= 2 x 10/13

= 20/13

a) 3/5 x 7/9 + 11/9 x 3/5 - 3/10

=  3/5 x 7/9 + 11/9 x 3/5 - 3/5 x 2

=  3/5 x ( 7/9 + 11/9 - 2 )

=  3/5 x 0

=  0

b) 14/13 : 1/2 + 3/13 x 2 - 2 x 7/13

=  14/13 x 2/1 + 3/13 x 2 - 2 x 7/13

=  ( 14/13 + 3/13 - 7/13 ) x 2

=  10/13 x 2 = 20/13

chẳng hiể gì cả

a)1/3+1/4+2/3+3/4

=(1/3+2/3)+(1/4+3/4)

=1+1

=2.

b)1/2+1/3-1/5+1/6

=(1/2+1/3+1/6)-1/5

=1-1/5

=4/5

c)2/3x4/5+1/3x4/5

=4/5x(2/3+1/3)

=4/5x1

=4/5

d)2/3x4/5-1/3x4/5

=4/5x(2/3-1/3)

=4/5x1/3

=4/15

cccccccccllllllllllllllllll

(x+5)+(x+6)+(x+7)+(x+8)=58

=> x+5+x+6+x+7+x+8=58

=> 4x+26=58

=> 4x=32

=> x=8

Vậy x=8

tk cho mk nha 

(bn mới lớp 5 à ,thế thì dấu " =>" là dấu suy ra)

*****Chúc bạn học giỏi*****

(x+5)+(x+6)+(x+7)+(x+8)=58

nên x+5+x+6+x+7+x+8=58

nên 4x+26=58

nên 4x=58-26=32

nên x=32:4=8

vậy x=8

x:4=7-3

x:4=4

x=4x4

x=16

Ai

x=16 đó

x:4=4

x=4x4

x=16