(3 1/7-n)+1 4/7=3 5/7+2/7

(3 1/7-n)+1 4/7=4

(3 1/7-n)=4-1 4/7

(3 1/7-n)=2 3/7

n=3 1/7-2 3/7=2 8/7-2 3/7=5/7

n=5/7

(3 1/7-n)+1 4/7 =3 5/7+2/7

 (3 1/7-n)+1 4/7 =26/7+2/7

  (3 1/7-n)+1 4/7=28/7 

(3 1/7-n) =28/7 - 1 4/7

 3 1/7-n)=28/7-11/7

 3 1/7-n)=17/7

-n=17/7-3 1/7

-n=17/7-22/7

-n=-5/7

n=5/7