12.8
1) 6 8/10 — 5 5/9 = 6 4/5 — 5 5/9 = 6 36/45 — 5 25/45 = 1 11/45= 56/45
2) 2 13/ 30 — 2 1/12 = 2 26/60 — 2 5/60 = 21/60 = 7/2
3) 56/45 : 7/20 · 3,6 = 56/45·20/7 ·36/10= 12,8
