`76,`
`a, 5 5/27 + 7/23 + 0,5 - 5/27 + 16/23`
`= ( 5 5/27 - 5/27 ) + ( 7/23 + 16/23 ) + 0,5`
`= 5 + 1 + 1/2`
`= 6 + 1/2`
`= 13/2`
`b, 3/8 . 27 1/5 - 51 1/5 . 3/8 + 19`
`= 3/8 . ( 27 1/5 - 51 1/5 ) + 19`
`= 3/8 . ( - 24 ) + 19`
`= ( - 9 ) + 19`
`= 10`
`c, 25 . ( - 1/5 )^3 + 1/5 - 2 . ( - 1/2 )^2 - 1/2`
`= 25 . ( - 1 )/125 + 1/5 - 2 . 1/4 - 1/2`
`= ( - 1 )/5 + 1/5 - 1/2 - 1/2`
`= ( ( - 1 )/5 + 1/5 ) - ( 1/2 + 1/2 )`
`= 0 - 1`
`= - 1`
`d, 35 1/6 : ( - 4/5 ) - 45 1/6 : ( - 4/5 )`
`= 35 1/6 . ( - 5 )/4 - 45 1/6 . ( - 5 )/4`
`= ( - 5 )/4 . ( 35 1/6 - 45 1/6 )`
`= ( - 5 )/4 . ( - 10 )`
`=25/2`
`77,`
`a, 1/5 + x = ( - 2 )/3`
`⇔ x = ( - 2 )/3 - 1/5`
`⇔ x = ( - 13 )/15`
Vậy `, x = ( - 13 )/15 .`
`b, - 5/8 + x = 4/9`
`⇔ x = 4/9 - ( - 5 )/8`
`⇔ x = 77/72`
Vậy `, x = 77/72 .`
`c, 1 3/4 . x + 1 1/2 = - 4/5`
`⇔ 7/4 . x + 3/2 = ( - 4 )/5`
`⇔ 7/4 . x = ( - 4 )/5 - 3/2`
`⇔ 7/4 . x = ( - 23 )/10`
`⇔ x = ( - 23 )/10 : 7/4`
`⇔ x = ( - 46 )/35`
Vậy `, x = ( - 46 )/35 .`
`d, x . ( 1/5 + 1/4 ) - ( 1/7 + 1/9 ) = 0`
`⇔ x . ( 1/5 + 1/4 ) = 1/7 + 1/9`
`⇔ x . ( 4/20 + 5/20 ) = ( 8/56 + 7/56 )`
`⇔ x . 9/20 = 15/56`
`⇔ x = 15/56 : 9/20`
`⇔ x = 25/42`
Vậy `, x = 25/42 .`
