Let 1/3x + y = a , and 1/3x - y = b ,
a + b = 3/4 -----------------> (1)
4a + 4b = 3 -------------> (1)
also ,
a/2 - b/2 = -1/8
(a - b)/2 = -1/8
a - b = -1/4
4a - 4b = -1 ---------------------------> (2)
Adding equations (1) and (2) :-
4a + 4b = 3
4a - 4b = -1
--------------------
8a = 2
a = 2/8
a = 1/4
4a - 4b = -1
4*1/4 - 4b = -1
1 - 4b = -1
4b = 1 + 1
4b = 2
b = 2/4
b = 1/2
1/3x + y = a
1/3x + y = 1/4
3x + y = 4 -----------------> (3)
1/3x - y = b
1/3x - y = 1/2
3x - y = 2 -----------------> (2)
Adding equations (3) and (4) :-
3x + y = 4
3x - y = 2
--------------------------
6x = 6
x = 1
3x + y = 4
3*1 + y = 4
y = 4 - 3 = 1
Hence,
x = 1 , y = 1