Răspuns :
a + b = 50
a - b = 10
a = 10 + b
10 + b + b = 50
10 + 2b = 50
2b = 50 - 10
2b = 40
b = 40 : 2
b = 20
a = 10 + 20 = 30
30 + 20 = 50
30 - 20 = 10
a - b = 10
a = 10 + b
10 + b + b = 50
10 + 2b = 50
2b = 50 - 10
2b = 40
b = 40 : 2
b = 20
a = 10 + 20 = 30
30 + 20 = 50
30 - 20 = 10