tính nhanh giúp e với nhanh lên ạ

`a, 21/47+9/35 +26/47+4/5`

`=( 21/47+26/47)+(9/35 +4/5)`

`=1+(9/35 +4/5)`

`=1+37/35`

`=72/35`

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`b, 15/12+5/13 -3/12-8/13`

`=( 15/12 -3/12)+(5/13 -8/13)`

`=1+(5/13 -8/13)`

`=1+(-3/13)`

`=10/13`

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`c, 3/8 . 19 1/3 -3/8. 33 1/3`

`= 3/8 .( 19 1/3 -33 1/3)`

`= 3/8 .(58/3 -100/3)`

`= 3/8 .(-14)`

`=-5,25`

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`d, (-5/6-2/5): 3/8+(4/5-11/30):3/8`

`=(-5/6-2/5). 8/3+(4/5-11/30). 8/3`

`=8/3. [(-5/6-2/5)+(4/5-11/30)]`

`=8/3. [-5/6-2/5+4/5-11/30]`

`=8/3. [(-2/5+4/5)+(-5/6-11/30)]`

`=8/3. [2/5+(-6/5)]`

`=8/3. (-4/5)`

`=-32/15`

`@Lynacute`