For this system of equations, you can easily use the elimination method because y cancels eachother out. Look below for work \.
x + y = 7 2 + y = 7 3(2) - y = 1
3x - y = 1 y = 5 6 - y = 1
-y = -5
4x = 8 y = 5
x = 2
Final Answer: x=2, y=5 OR (2, 5)
Hope this helps!! :)