ai bt làm giúp mình vs

Đáp án `+` Giải thích các bước giải:

a) `(-2)/15 + (-8)/15 + 3/5`

`= (-2)/15 + (-8)/15 + 9/15`

`= [(-2) + (-8) + 9]/15` 

`= [(-10) + 9]/15 `

`= (-1)/15.`

b) `-1/3 + 2/5 + (-5)/2`

`= -10/30 + 12/30 + (-75)/30`

`= [(-10) + 12 + (-75)]/30`

`= [2 + (-75)]/30`

`= (-73)/30.`

c) `(2 + 3/5) : (2/5 - 1/5)`

`= (2/1 + 3/5) : 1/5`

`= (10/5 + 3/5) : 1/5`

`= 13/5 : 1/5`

`= 13/5 . 5/1`

`= 13/1 . 1/1`

`= 13.`

d) `((-5)/7 + 1/2) : 3/28`

`= ((-10)/14 + 5/14) . 28/3`

`= (-5)/14 . 28/3`

`= (-5)/1 . 2/3`

`= (-10)/3.`

2.

a) `5/7 . x - 1/2 = 5/14`

`5/7 . x = 5/14 + 1/2`

`5/7 . x = 5/14 + 7/14`

`5/7 . x = 12/14`

`x = 12/14 : 5/7`

`x = 12/14 . 7/5`

`x = 12/2 . 1/5`

`x = 12/10`

`x = 6/5`

b) `5/3 : x - 1/5 = (-7)/5`

`5/3 : x = (-7)/5 + 1/5`

`5/3 : x = (-6)/5`

`x = 5/3 : (-6)/5`

`x = 5/3 . (-5)/6`

`x = 5/3 . (-5)/6`

`x = -25/18`