sos cần gấp lắm cần gấp lắm

Câu `1:`

`1)`

`a) 4/5 - 3/5 : (1 - 2/3)`

`= 4/5 - 3/5 : 1/3`

`= 4/5 - 3/5 * 3`

`= 4/5 - 9/5`

`= (-5)/5 = - 1`

`----------------`

`b) 3/13 * 15/11 + 3/11 * 7/13 - 3/13`

`= 3/11 * 15/13 + 3/11 * 7/13 - 3/13`

`= 3/11 * (15/13 + 7/13) - 3/13`

`= 3/11 * 22/13 - 3/13`

`= 6/13 - 3/13`

`= 3/13`

`----------------`

`2)`

`a) x/6 - 1/2 = 2/3`

`=> x/6 = 2/3 + 1/2`

`=> x/6 = 4/6 + 3/6`

`=> x/6 = 7/6`

`=> x = 7`

Vậy `x = 7`

`---------------`

`b) 0,75x - 0,2x = 2,75`

`=> 0,55x = 2,75`

`=> x = 2,75 : 0,55`

`=> x = 5`

Vậy `x = 5`

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