To simplify this, we first convert the mixed numbers to improper fractions:

2/5 = 10/5 = 2

1 1/4 = 1 + 1/4 = 4/4 + 1/4 = 5/4

1 1/3 = 1 + 1/3 = 3/3 + 1/3 = 4/3

Now we have:

(2 - 6/6) : (5/4 - 4/3)

2 - 1 : 5/4 - 4/3

1 : (15/12 - 16/12)

1 : (-1/12)

Therefore, the result is 1 : -1/12 or simply 1 : -1/12.