`a)`
`(-0,35) . 3/14 . (-3 5/7) . (-4/21)`
`= -7/20 . 3/14 . (-26)/7 . (-4)/21`
` = - (7/20 . 3/14 . 26/7 . 4/21)`
` = - (7.3.26.4)/(20.14.7.21)`
`= -(7 . 3.13.3.4)/(4.5.2.7.7.3.7)`
` = (-13)/(5.7.7)`
` = -13/245`
``
`b) (-3/7) . 5/11 + (-5/14) . 5/11`
` = 5/11 . (-3/7 - 5/14)`
` = 5/11 . (-6/14 - 5/14)`
` = 5/11 . (-11)/14`
` = -5/14`
``
`c) 15 - 2 1/3 : (4/9 -1/6)`
` = 15 - 7/3 : 5/18`
` = 15 - 42/5`
` = 33/5`
``
`d) (-3/4 + 2/5) : 3/7 + (3/5 +(-1)/4 ) : 3/7`
` = (-3/4 + 2/5) . 7/3 + (3/5 - 1/4) . 7/3`
` = (-3/4 + 2/5 + 3/5 - 1/4) . 7/3`
`= (-1 + 1) . 7/3`
`= 0 . 7/3`
` = 0`
