To solve this expression, we first need to simplify the terms inside the parentheses.

6 3/4 - 5 1/8 = (27/4) - (41/8)
= (54/8) - (41/8)
= (13/8)

Now, we have:
(13/8 : 1 9/32) : 2 1/5

Converting the mixed numbers to improper fractions:

1 9/32 = (32 + 9)/32 = 41/32
2 1/5 = (5*2 + 1)/5 = 11/5

(13/8 : 41/32) : 11/5
= (13/8 : 41/32) x 5/11
= (13/8 x 32/41) x 5/11
= (416/328) x (5/11)
= 2.4 x 0.454545
= 1.090909

Therefore, (6 3/4 - 5 1/8 : 1 9/32) : 2 1/5 = 1.090909