Respuesta :

musiclover10045

x +y = 20 ( rewrite as x = 20-y)

3x - 3y =30

3(20-y) - 3y = 30

60-3y - 3y = 30

60-6y = 30

-6y = -30

y = -30 / -6 = 5

x=20-5 = 15

x = 15, y = 5