`a) 2/3 + (-1/8) . 4/3`
` = 2/3 + (-1/6)`
` = 4/6 + (-1/6)`
` = 1/2`
`B) (-3/5) . 5/7 + (-3/5) . 4/7 - (-3/5)`
` = (-3/5) . (4/7 + 5/7) + 3/5`
` = (-3/5) . 9/7 + 3/5`
` = -27/35 + 3/5`
` = 6/35`
`c) 75% - 1 1/2 + 0,5 : 5/12`
` = 3/4 - 3/2 + 1/2 : 5/12`
` = 3/4 - 6/4 + 1/2 . 12/5`
` = -3/4 + 6/5`
` = 9/20`