(7 1/8-х)+2 3/8=5 7/8
7 1/8-х=5 7/8-2 3/8
7 1/8-х=3 4/8
х=7 1/8- 3 4/8
х=6 9/8- 3 4/8
х=3 5/8
57/8-х+19/8=47/8
-х=47/8-199/8-57/8
-х=-72/8
х=72/8
х=9
Ответ:9.