If you would like to solve the system of equations, you can do this using the following steps:
x = y - 3
x + 3y = 13 ... y - 3 + 3y = 13
___________
y - 3 + 3y = 13
4y = 13 + 3
4y = 16
y = 4
x = y - 3 = 4 - 3 = 1
(x, y) = (1, 4)
The correct result would be A) (1, 4).