Răspuns :
a ___/___/___/
b ___/
20 : 2 = 10
b = 10
a - 10 = 20
a = 30
sau
a - b = 20
a = 3b
3b - b = 20
b = 20 : 2
b = 10
a = 3 * 10
a = 30
b ___/
20 : 2 = 10
b = 10
a - 10 = 20
a = 30
sau
a - b = 20
a = 3b
3b - b = 20
b = 20 : 2
b = 10
a = 3 * 10
a = 30