Odpowiedź :
x-y = 30
x = 3y
x = 30+y
x = 3y
2x = 30+y+3y
2x = 30+4y
x = 15+2y
x = 45
y = 15
x = 3y
x = 30+y
x = 3y
2x = 30+y+3y
2x = 30+4y
x = 15+2y
x = 45
y = 15