`a)-7/813 + 496 . (-7/813) + (-7/813) . 316`
`= -7/813 . ( 1 + 496 + 316)`
`= -7/813 . 813`
`= -7`
`b) -9/10 . 5/14 + 1/10 . (-9/2) + 1/7 . (-9/10)`
`= -9/10 . ( 5/14 + 1/7) + 1/10 . (-9/2) `
`= -9/10 . 1/2 + 1/10 . (-9/2)`
`= -9/10 . 1/2 + -9/10 . 1/2`
`=-9/10 . ( 1/2 + 1/2)`
`= -9/10 . 1`
`=-9/10`
`c) 12/19 . 7/5 . -13/17 . 19/12 . 17/13`
`= ( 12/19 . 19/12) . ( -13/17 . 17/13) . 7/5`
`= 1 . (-1) . 7/5`
`= (-1) . 7/5`
`= -7/5`
`d) 75/100 + 1,1 : ( 2/5 - 1 1/2) - (1/3)²`
`= 3/4 + 11/10 : ( 2/5 - 3/2) - 1/9`
`= 3/4 + 11/10 : (-11/10) - 1/9`
`= 3/4 + (-1) - 1/9`
`= 27/36 + (-36/36) - 4/36`
=`\frac{27 + (-36) - 4}{36}`
`= -13/36`