b) { ( a - 416 : 4 + 2 ) × 5 + 3 } × 2 = 1986
{ ( a - 104 + 2 ) × 5 + 3 } × 2 = 1986
( a - 104 + 2 ) × 5 + 3 = 1986 : 2
( a - 104 + 2 ) × 5 + 3 = 993
( a - 104 + 2 ) × 5 = 993 - 3
( a - 104 + 2 ) × 5 = 990
a - 104 + 2 = 990 : 5
a - 104 + 2 = 198
a - 104 = 198 - 2
a - 104 = 196
a = 196 + 104
a = 300
c) { ( a - 1 ) : 100 + 90 } : 10 - 10 = 0
{ ( a - 1 ) : 100 + 90 } : 10 = 0 + 10
{ ( a - 1 ) : 100 + 90 } : 10 = 10
( a - 1 ) : 100 + 90 = 10 × 10
( a - 1 ) : 100 + 90 = 100
( a - 1 ) : 100 = 100 - 90
( a - 1 ) : 100 = 10
a - 1 = 10 × 100
a - 1 = 1000
a = 1000 + 1
a = 1001
