r + g + a = 700 ; ( 1 )
a - 8 = 2( g - 6 ) ;
g - 6 = 2( r - 7 ) ; atunci g = 2r - 8 ; ( 2 )
si, a - 8 = 2 × 2( r - 7 ) => a = 4r - 20 ; ( 3 )
Din ( 1 ), ( 2 ) si ( 3 ) => 7r - 28 = 700 <=> 7r = 728 <=> r = 728 ÷ 7 <=> r = 104 ;
g = 2 × 104 - 8 => g = 208 - 8 => g = 200 ;
a = 4 × 104 - 20 => a = 416 - 20 => a = 396 ;
Bafta !