`a) ( 2 3/7 +1 5/6) - 3/7`
`= 2 3/7 + 1 5/6 - 3/7`
`= ( 2 3/7 - 3/7) + 1 5/6`
`= 2 + 1 5/6`
`= 3 5/6`
`= 35/6`
$\\$
`b) ( (-5)/16 + 25% + 5/8) : (-2 1/4)`
`=-1/4 : (-9/4)`
`= -1/4 . (-9/4)`
`= -1/4`
`c) -3/25 : 3 - 3/25 : 4/7 + |(-5)/9|`
`= -3/25 . 1/3 + (-3)/25 . 7/4 + 5/9`
`= -3/25 . ( 1/3 + 7/4) + 5/9`
`= -3/25 . 25/12 + 5/9`
`= -1/4 + 5/9`
`= 11/36`