\(\dfrac{4}{27}+\dfrac{5}{9}+\dfrac{13}{9}-2\\ =\dfrac{4}{27}+\dfrac{18}{9}-2\\ =\dfrac{4}{27}+\dfrac{18\times3}{9\times3}-\dfrac{2\times27}{27}\\ =\dfrac{4}{27}+\dfrac{54}{27}-\dfrac{54}{27}\\ =\dfrac{4}{27}\)

`a: =(7/3-4/3)+11/5=16/5`

`b: =(18/13-5/13)+55/46=1+55/46=101/46`

`c: =27/25-4/9-2/25+5/9=(27/25-2/25)+(5/9-4/9)=1+1/9=10/9`

a, 2/5 + 1/6 + 3/5

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

=        5/5 + 1/6

=          1 + 1/6

=         6/6 + 1/6 

=            7/6

b, 9/13 + 4/13 + 2/3

=        13/13    + 2/3

=            1 + 2/3

= 3/3 + 2/3

=             5/3

2/5+1/6+3/5

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

=5/5+1/6

=1+1/6

=7/6

9/13+4/13+2/3

=(9/13+4/13)+2/3

=13/13+2/3

=1+2/3

=5/3

k mk nha các bạn, nhớ kb mk đó

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

                   =1+1/6=7/6

9/13+4/13+2/3

=(9/13+4/13)+2/3

=1+2/3=5/3

a: =20/90+15/90+54/90=89/90

b: =(9/13+4/13)+2/3=1+2/3=5/3

`7/13+5/9+6/13+5/9`

`=(7/13+6/13)+(5/9+5/9)`

`=13/13+10/9`

`=1+10/9`

`=9/9+10/9`

`=19/9`

19/9

=5/13x(4/5-9/15)

=5/13x1/5

=1/13

???????????????????????????????????????

cấp mấy đấy

C1: 45 - 9 . ( 13 + 5 )

= 45 - 9 . 18

= 45 - 162

= -117

C2: 45 - 9 . ( 13 + 5 )

= 45 - 9 . 13 - 9 . 5

= 45 - 117 - 45

= -117

c1 : 36 : 18

=2

c2 ko biết

C1: =45-9.18=45-162=-117

C2: =45-9.13+9.5=45-117+45=-117

**** cho mik nha!