(3 1/7-n)+1 4/7=3 5/7+2/7 (3 1/7-n)+1 4/7=3 7/7 (3 1/7-n)=3 7/7-1 4/7 (3 1/7-n)=2 3/7 -п=3 1/7-2 3/7 -п=2 8/7-2 3/7 -п=5/7 п=-5/7