Verified answer

x - 3y = 1

3x + y = 13

Метод подстановки

x = 1 + 3y

3(1 + 3y) + y = 13

3 + 9y + y = 13

10y = 10

y = 1

3x + 1 = 13

3x = 12

x = 4

ответ (4, 1)