\(a,\dfrac{5}{9}\times\dfrac{5}{2}+\dfrac{4}{9}\times\dfrac{5}{2}=\dfrac{5}{2}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)=\dfrac{5}{2}\times1=\dfrac{5}{2}\)

\(12\times\dfrac{3}{4}-\dfrac{3}{4}\times\dfrac{12}{7}=\dfrac{3}{4}\times\left(12-\dfrac{12}{7}\right)=\dfrac{3}{4}\times\dfrac{72}{7}=\dfrac{54}{7}\)

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) 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

\(\frac{5}{9}:\frac{4}{7}+\frac{13}{9}\cdot\frac{7}{4}\)

\(=\frac{5}{9}\cdot\frac{7}{4}+\frac{13}{9}\cdot\frac{7}{4}\)

\(=\left(\frac{5}{9}+\frac{13}{9}\right)\cdot\frac{7}{4}\)

\(=2\cdot\frac{7}{4}\)

\(=\frac{14}{4}\)

=\(\frac{5}{9}\)*\(\frac{7}{4}\)+\(\frac{13}{9}\)*\(\frac{7}{4}\)

=\(\frac{7}{4}\)*(\(\frac{5}{9}+\frac{13}{9}\))

=\(\frac{7}{4}\)*2

=\(\frac{7}{2}\)

3/2 + 4/9 + 4/7 + 5/9 = 43/14

\(\frac{2}{9}+\frac{1}{5}+\frac{7}{9}+\frac{4}{5}=\left(\frac{2}{9}+\frac{7}{9}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)=\frac{9}{9}+\frac{5}{5}=1+1=2\)

\(\frac{2}{9}+\frac{1}{5}+\frac{7}{9}+\frac{4}{5}=\left(\frac{2}{9}+\frac{7}{9}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)=1+1=2\)

=(2/8+7/9)+(1/5+4/5)

=1+1=?

(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

= 17/7 + 4/7 - 2/5 + 3/5

= 21/7 - 5/5

= 3 - 1

= 2