Tìm x a/ 1 2/3 x X = 2 3/5

`a)1 2/3xx x=2 3/5`

`5/3xx x=13/5`

`x=13/5:5/3`

`x=13/5xx3/5`

`x=39/25`

Vậy `x=39/25`

___________________________

`b)x+3,2=376:100`

`x+3,2=3,76`

`x=3,76-3,2`

`x=0,56`

Vậy `x=0,56`

___________________________

`c)(123:x)-0,4=11,9`

`123:x=11,9+0,4`

`123:x=12,3`

`x=123:12,3`

`x=10`

Vậy `x=10`