tinh 12 phan 35 + 21phan 25 =         ,34 phan 12 + 5 phan 6=          ,23 phan 56 - 9 phan 56 =             ,21 phan 10- 5 phan10=              ,1 phan 4 nhan 4 phan 5=

`12/35+21/25`

`=60/175+147/175`

`=207/175`

`34/12+5/6`

`=17/6+5/6`

`=22/6`

`=11/3`

`23/56-9/56`

`=14/56`

`=1/4`

`21/10-5/10`

`=16/10`

`=8/5`

`1/4xx4/5`

`=1/5`

#wheijx.

`12/35 + 21/25 = 300/875 + 735/875 = 1035/875 = 207/175`

`34/12 + 5/6 = 34/12 + 10/12 = 44/12 = 11/3`

`23/56 - 9/56 = (23-9)/56 = 14/56 = 1/4`

`21/10 - 5/10 = (21-5)/10 = 16/10 = 8/5`

`1/4 xx 4/5 = (1xx4)/(4xx5) = 1/5`