Răspuns :
7 + 7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } : 7 - 7 = 9
7 + 7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } : 7 = 9 + 7
7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } : 7 = 16 - 7
7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } = 9 × 7
7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 = 63 : 7
7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 = 9
7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] :7= 9 + 7 - 7
7 +7 x( 7 x a :7 + 7 ) :7 - 7 = 9 × 7:7
7 +7 x( 7 x a :7 + 7 ) :7 - 7 = 9
7 x( 7 x a :7 + 7 ) :7 = 9 + 7 - 7
7 x( 7 x a :7 + 7 ) :7 = 9
7 x a :7 + 7 = 9 × 7 : 7
7 x a : 7 = 9 - 7
7 x a = 2 × 7
7 x a = 14
a = 14 : 7
a = 2
7 + 7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } : 7 = 9 + 7
7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } : 7 = 16 - 7
7 x { 7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 } = 9 × 7
7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 = 63 : 7
7 + 7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] : 7 - 7 = 9
7 x [ 7 +7 x( 7 x a :7 + 7 ) :7 - 7 ] :7= 9 + 7 - 7
7 +7 x( 7 x a :7 + 7 ) :7 - 7 = 9 × 7:7
7 +7 x( 7 x a :7 + 7 ) :7 - 7 = 9
7 x( 7 x a :7 + 7 ) :7 = 9 + 7 - 7
7 x( 7 x a :7 + 7 ) :7 = 9
7 x a :7 + 7 = 9 × 7 : 7
7 x a : 7 = 9 - 7
7 x a = 2 × 7
7 x a = 14
a = 14 : 7
a = 2