Răspuns :
a + b = 70
a - b = 12
a = 12 + b
12 + b + b = 70
12 + 2 × b = 70
2 × b = 70 - 12
2 × b = 58
b = 58 : 2
b = 29
a = 12 + 29
a = 41
a + b = 70
a - b = 12
a = 12 + b
12 + b + b = 70
12 + 2 × b = 70
2 × b = 70 - 12
2 × b = 58
b = 58 : 2
b = 29
a = 12 + 29
a = 41