Look aside,

x+y=8.........①

m-n=6........②

Looking vertically,

x+m= 13.....③

y+n=8........④

From ① ④, x = n.

From ②, m=n+6.

Substitute ③ to get:

x+(6+n)= 13

2n=7

n=3.5

So,

x=3.5

m=9.5

y=4.5