We have
[tex]
x+3y=7 \\
x-3y=1[/tex].
First we add the equations to get rid of 3y terms and solve for x.
[tex]2x=8\Longrightarrow x=4[/tex]
Then we insert our x into either of the equations and solve for y.
[tex]4+3y=7\Longrightarrow y=1[/tex]
The answer is A.
Hope this helps.
