Notam a,b,c numerele si X nr care se adauga
a+b+c = 134
a+X = 48 => a= 48-X
b+X = 53 => b = 53-X
c+X = 69 => c = 69-X
48-X+53-X+69-X = 134
3×X = 170-134
3×X = 36
X = 36:3
X = 12
a = 48-12 = 36
b = 53-12 = 41
c = 69-12 = 57
Verificare:
36+41+57 = 134
Numerele sunt: 36; 41; 57.