First of all we can cross out C because the lines are not overlapping, and we can also cross out D because they are not parallel. 
To chose between A and B simply plug in the values for x and attempt to solve. 
(A) 4
3 * (4) + 2 * y = 8
=> 12 + 2 * y = 8
=> 2 * y = -4
=> y = -2
Then plug x and y into the second equation. 
3 * (4) + 2 * (-2) = 8
=> 12 + (-4) = 8
=> 8 = 8
This means that the x value of 4 works for the system. 
Final answer: 
(A) 4. 
Hope I helped :)