a + b + c + d = 1 026
a + b = 549
a + b + c = 911
b + c + d = 796
_________________
1 026 - 911 = 115 ( d)
911 - 549 = 362 ( c)
b + c + d = 796
b + 362 + 115 = 796
b + 477 = 796
b = 796 - 477
b = 319
a + b = 549
a + 319 = 549
a = 549 - 319
a = 230 ( a)
Verific: 230 + 319 + 362 + 115 = 1 026 → suma celor 4 numere