cứu ......... deadline từ hè

d) x -`1/5` = `7/11` . `3/21`

    x - `1/5`= `1/11`

             x = `1/11` + `1/5`

             x = `16/55`

Vậy x =`16/55`

e) `x/25` = `-3/15` . `7/6`

     `x/25`= `-7/30`

            x = `-7/30` . 25

            x =`-35/6`

Vậy x = `-35/6`