2/6(5b-4a)+1/5, при a=5, и b=6
2/6 (5 х 6 - 4 х 5) + 1/5 = 2/6 (30 -20) + 1/5 = 2/6 х 10 + 1/5 = 10/3 + 1/5 = (50/15 + 3/15 = 53/15 = 3 целых 8/15