a) `1 1/8 . 11/4 - 9/8 . 0,75`
`= 9/8 . 11/4 - 9/8 . 3/4`
`=9/8 ( 11/4 - 3/4)`
`= 9/8 . 2`
`=9/4`
$\\$
b) `1,4 . 15/49 - ( 3/5 + 3/7) : 7 1/5`
`= 7/5 . 15/49 - ( 3/5 + 3/7) .5/36`
`= 7/5 . 15/49 -1/12 - 5/84`
`= 3/7 - 1/12 - 5/84`
`=36/84 - 7/84 - 5/84`
`= 29/84 - 5/84`
`=2/7`