`Bài` `2:`

`a)6/7xx16/15xx7/6xx21/32`

`=(6/7xx7/6)xx(16/15xx21/32)`

`=1xx7/10`

`=7/10`

`b)21/17xx13/14xx56xx3/42`

`=21/17xx13/14xx56xx1/14`

`=(21/17xx13/14)xx(56xx1/14)`

`=(21/17xx13/14)xx56/14`

`=39/34xx4`

`=78/17`

`c)7/4xx11/21+11/21xx5/4`

`=11/21xx(7/4+5/4)`

`=11/21xx12/4`

`=11/7`

`d)23/14xx6/13-9/14xx6/13`

`=6/13xx(23/14-9/14)`

`=6/13xx14/14`

`=6/13xx1`

`=6/13`

`#BTS`

`a) 6/7 xx16/15 xx 7/6 xx21/32`

`=(6/7 xx7/6) xx(16/15 xx 21/32)`

`=1 xx 7/10`

`=7/10`

`b) 21/17 xx 13/14 xx56 xx3/42`

`=21/17 xx 13/14 xx56 xx1/14`

`= (21/17 xx13/14) xx(56/14)`

`= 39/34 xx 4`

`=78/17`

`c) 7/4 xx11/21+11/21 xx5/4`

`=11/21 xx(7/4 +5/4)`

`=11/21 xx 12/4`

`=11/7`

`d) 23/14 xx6/13 -9/14 xx6/13`

`=(23/14 -9/14) xx6/13`

`=14/14 xx6/13`

`=1 xx6/13`

`=6/13`