`a) 1/10 - 1/2 + 7/5`
`= 1/10 - 5/10 + 14/10`
`= \frac{1-5 + 14}{10}`
`= 1`
$\\$
`a) 1/10 - 2/7 + 7/5`
`= 7/70 - 20/70 + 98/70`
`= \frac{7 - 20 + 98}{70}`
`= 17/14`
$\\$
`b) -6/11 . 8/17 + \frac{-6}{11} . 9/17 + \frac{-5}{11}`
`= \frac{-6}{11} . ( 8/17 + 9/17) + \frac{-5}{11}`
`= \frac{-6}{11} . 1 + \frac{-5}{11}`
`= \frac{-6}{11} + \frac{-5}{11}`
`= (-1)`
$\\$
`c) 7 5/9 - ( 2 5/9 - 1 4/7)`
`= 7 5/9 - 2 5/9 + 1 4/7`
`= (7 5/9 - 2 5/9) + 1 4/7`
`= 5 + 1 4/7`
`= 6 4/7`
`= 46/7`
$\\$
`d) 2/3 . 2/5 + 25% - 0,7 : 6/5`
`= 2/3 . 2/5 + 1/4 - 7/10 . 5/6`
`= 4/15 + 1/4 - 7/12`
`= 16/60 + 15/60 - 35/60`
`= \frac{16 + 15 - 35}{60}`
`= -1/15`
