`1/2 . ( - 3 )/4 . ( - 5 )/8 . ( - 8 )/9`
`= ( 1/2 . ( - 3 )/4 ) . ( ( - 5 )/8 . ( - 8 )/9 )`
`= ( - 3 )/8 . 5/9`
`= ( - 5 )/24`
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`6/5 + 1/6 : ( - 3 )`
`= 6/5 + 1/6 . ( - 1 )/3`
`= 6/5 + ( - 1 )/18`
`= 108/90 + ( - 5 )/90`
`= 103/90`
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`7/8 : 5/4 . ( - 10 )/7`
`= 7/8 . 4/5 . ( - 10 )/7`
`= ( 7 . 4 . ( - 10 ) )/( 8 . 5 . 7 )`
`= ( 7 . 4 . ( - 2 ) . 5 )/( 2 . 4 . 5 . 7 )`
`= - 1`