`k) -23/39 . \frac{-13}{56} . 70/23 : 125/75`
`= 23/168 . 70/23 . 75/125`
`= 5/12 . 3/5`
`= 1/4`
--------------------------------------------------------
bài 2)
`a) -1/10 + 2/5 x + 7/20 = 1/10`
`-1/10 + 2/5 x = 1/10 - 7/20`
`-1/10 + 2/5x = -1/4`
`2/5x = -1/4 - (-1/10)`
`2/5x = -3/20`
`x = -3/20 : 2/5`
`x = -3/8`
-------------------------------------------------------------
`b) 1/3 + 1/2 : x = -1/5`
`1/2 : x = -1/5 - 1/3`
`1/2 : x =-8/15`
`x = 1/2 : (-8/15)`
`x = -15/16`
--------------------------------------------------------
`c)-2/3 : x + 5/8 = -7/18`
`-2/3 : x = -7/18 - 5/8`
`-2/3 : x =-73/72`
`x = -2/3 : -73/72`
`x = 48/73`
