3a+b=19=>a=(19-b)/3 (1)
2b+2d=36=>d=(36-2b)/2 (2)
din (1),(2) si 2a+b+d=26 =>2(19-b)/3+b+(36-2b)/2=26
=>2*2(19-b)+6b+3(36-2b)=6*26=>4*19-4b+6b+3*36-6b=156
=>76+108-156=4b=>b=(184-156)/4=>b=28/4=>b=7
dar a=(19-b)/3=>a=12/3=>a=4
dar d=(36-2b)/2=>d=(36-14)/2=>d=11
dar a+2c+b=29=>c=(29-7-4)/2=>c=9
sa verificam si celelalte ecuatii
a+2d+b=4+2*11+7=>a+2d+b=33
2d+b+c=2*11+7+9=>2d+b+c=22+16=>2d+b+c=38
