Câu 7:

`( (-3)/4 + 2/5) : 3/7 + (3/5 + (-1)/4) : 3/7`

` = ( (-3)/4 + 2/5) . 7/3 + (3/5 - 1/4) . 7/3`

` = ( (-3)/4 + 2/5 + 3/5 - 1/4) . 7/3`

` = [ ( (-3)/4 - 1/4) +  (2/5 + 3/5)] . 7/3`

` = [ (-1) + 1] . 7/3`

` = 0 . 7/3 = 0`

Câu 8:

`(4/5 + (-9)/7) : 2021/2022 + ( (-5)/7 - (-6)/5 ) : 2021/2022`

` = (4/5 - 9/7) . 2022/2021 + (-5/7 + 6/5) . 2022/2021`

` = 2022/2021 . (4/5 - 9/7 - 5/7 + 6/5)`

` = 2022/2021 . [(4/5 + 6/5) - (9/7 + 5/7)]`

` = 2022/2021 . (2 - 2) = 0`

Câu 9:

`(-11)/24 : 17/23 - 11/24 : 17/11 - 1/12`

` = (-11)/24 . 23/17 - 11/24 . 11/17 - 1/12`

` = 11/24 . (-23)/17 - 11/24 . 11/17 - 1/12`

`= 11/24 . (-23/17 - 11/17) - 1/12`

` = 11/24 . (-2) - 1/12`

` = -11/12 - 1/12 = -1`

Câu 10:

`11/8 . [ ( (-5)/11 : 13/8 - 5/11 : 13/5) + (-6)/33] + (-3)/4`

` = 11/8 . [( (-5)/11 . 8/13 - 5/11 . 5/13) - 6/33] - 3/4`

` = 11/8. [( 5/11 . (-8)/13 - 5/11 . 5/13) - 6/33] - 3/4`

` = 11/8 . [ 5/11 . (-8/13 - 5/13) - 2/11] - 3/4`

` = 11/8 . [ 5/11 . (-1) - 2/11] - 3/4`

` = 11/8 . (-5/11 - 2/11) - 3/4`

` = 11/8 . (-7/11) - 3/4`

` = -7/8 - 3/4`

` = -7/8 - 6/8 = -13/8`

Câu 11:

`A = (50 - 4/13 + 2/15 - 2/17)/(100 - 8/13 + 4/15 - 4/17)`

` = (50 - 4/13 + 2/15 - 2/17)/(2(50 - 4/13 + 2/15 - 2/17))`

` = 1/2`