12-(х+4 7/15)=5 13/15

12-(х+4 7/15)=5 13/1512 - x - 4 7/15 = 5 13/1512 - 4 7/15 + 5 13/15 = x180/15 - 67/15 + 88/15 = xx = 201/15 = 13.4