a+b+c+d=110
a-b=13 => a=b+13
c+d=77; c:d=6 => c=6d
b+13+b+77=110
2b+90=110
2b=110-90 => 2b=20 => b=20:2 => b=10
a=b+13 => a=10+13 => a=23
c+d=77 => 6d+d=77 => 7d=77 => d=77:7 => d=11
c=6d => c=6x11 => c=66
Numerele sunt: a=23; b=10; c=66; d=11
verificam:23+10+66+11=110
