12 2/7+5 5/14-4 5/7; 4 1/7+5 4/9-1 1/7-1 1/3:

12 2/7+5 5/14-4 5/7=86/7+75/14-33/7=(86*2+75*1-33*2)/14=(172+75-66)/14=181/14=12 13/144 1/7+5 4/9-1 1/7-1 1/3=29/7+49/9-8/7-4/3=(29*9+49*7-8*9-4*21)/63=(261+343-72-84)/63=448/63=64/9=7 1/9