Răspuns :
( a - 20 ) : 7 + 3104 - 999 = 2108
( a - 20 ) : 7 + 3104 = 2108 + 999
( a - 20 ) : 7 + 3104 = 3107
( a - 20 ) : 7 = 3107 - 3104
( a - 20 ) : 7 = 3
a - 20 = 3 × 7
a - 20 = 21
a = 21 + 20
a = 41 => numărul aflat
( a - 20 ) : 7 + 3104 = 2108 + 999
( a - 20 ) : 7 + 3104 = 3107
( a - 20 ) : 7 = 3107 - 3104
( a - 20 ) : 7 = 3
a - 20 = 3 × 7
a - 20 = 21
a = 21 + 20
a = 41 => numărul aflat
{[(x-20):7]+3104}-999=2108
[(x-20):7]+3104=2108+999
[(x-20):7]+3104=3107
(x-20):7=3107-3104
(x-20):7=3
x-20=3•7
x-20=21
x=20+21
x=41
[(x-20):7]+3104=2108+999
[(x-20):7]+3104=3107
(x-20):7=3107-3104
(x-20):7=3
x-20=3•7
x-20=21
x=20+21
x=41