`1,`
`a, 2/3 . ( - 2 )/9 - 5/6 . 2/9`
`= ( - 2 )/3 . 2/9 - 5/6 . 2/9`
`= 2/9 . ( ( - 2 )/3 - 5/6 )`
`= 2/9 . ( - 3 )/2`
`= ( - 1 )/3`
`b, | ( - 5 )/6 | + 16 2/7 : ( - 3 )/5 - 28 2/7 : ( - 3 )/5`
`= 5/6 + 16 2/7 . ( - 5 )/3 - 28 2/7 . ( - 5 )/3`
`= 5/6 + ( - 5 )/3 . ( 16 2/7 - 28 2/7 )`
`= 5/6 + ( - 5 )/3 . ( - 12 )`
`= 5/6 + 20`
`= 125/6`