a, 20 . ( 231 + 69 ) + 72 . ( 231 + 69 )
= 20 . 300 + 72 . 300
= ( 20 + 72 ) . 300
= 92 . 300
= ( 90 + 2 ) . 300
= 90 . 300 + 2 . 300
= 27000 + 600
= 27600
b, 2017 - { 52 . 22 - 11 [ 72 - 5 . 23 + 8 . ( 112 - 121 ) ] }
= 2017 - { 52 . 22 - 11 [ 72 - 5 . 23 + 8 . 0 ] }
= 2017 - { 52 . 22 - 11 [ 49 - 5 . 8 + 0 ] }
= 2017 - { 52 . 22 - 11 [ 49 - 40 ] }
= 2017 - { 52 . 22 - 11 . 9 }
= 2017 - { 25 . 4 - 99 }
= 2017 - { 100 - 99 }
= 2017 - 1 = 2016
c, 10 - { [ ( x : 3 + 17 ) : 10 + 3 . 24 ] : 10 } = 5
[ ( x : 3 + 17 ) : 10 + 3 . 24 ] : 10 = 5
[ ( x : 3 + 17 ) : 10 + 3 .24 ] = 5 . 10
( x : 3 + 17 ) : 10 + 3 . 16 = 50
( x : 3 + 17 ) : 10 + 48 = 50
( x : 3 + 17 ) : 10 = 50 - 48
( x : 3 + 17 ) : 10 = 2
x : 3 + 17 = 2 . 10
x : 3 + 17 = 20
x : 3 = 20 - 17
x : 3 = 3
=> x = 3 . 3
=> x = 9
Vậy x = 9