(х-3 9/13)+5 10/13=12 4/13

(х-3 9/13)+5 10/13=12 4/13
х=12 4/13-5 10/13+3 9/13
х=10 3/13
(10 3/13-3 9/13)+5 10/13=6 7/13 +5 10/13=
=11 17/13=12 4/13
12 4/13=12 4/13