`a) ( 7 - 3/4 + 1/3 ) - ( 6 + 5/4 - 4/3 )`
`= 7 - 3/4 + 1/3 - 6 - 5/4 + 4/3`
`= ( 7 - 6 ) - ( 3/4 + 5/4 ) + ( 1/3 + 4/3 )`
`= 1 + 2 + 1`
`= 4`
`b) 7/8 : ( 2/9 - 1/18 ) + 7/8 : ( 1/36 - 5/12 )`
`= 7/8 : ( 4/18 - 1/18 ) + 7/8 : ( 1/36 - 15/36 )`
`= 7/8 : 1/6 + 7/8 : ( - 7 )/18`
`= 7/8 . 6 + 7/8 . ( - 18 )/7`
`= 7/8 . ( 6 + ( - 18 )/7 )`
`= 7/8 . 24/7`
`= 3`
`c) 3/5 . 13/46 - 1/10 . 16/23`
`= 3 . 1/5 . 1/2 . 13/23 - 1/10 . 16/23`
`= 39/23 . 1/10 - 1/10 . 16/23`
`= 1/10 . ( 39/23 - 16/23 )`
`= 1/10 . 1 = 1/10`
