First we need to simplify the given expression step by step:

Step 1: Calculate the value inside the parentheses
6,6 - 3 3/14 = 6 56/14 - 3 3/14
6 56/14 - 3 3/14 = 6 53/14

Step 2: Calculate the value of the expressions inside the parentheses
6 53/14 5 5/6 = (614 + 53) (56 + 5)/(146)
= (84 + 53)(30 + 5)/84
= 137*35/84

Step 3: Calculate the value of (21 - 1.25)
= 19.75

Step 4: Calculate the value of the expression within the innermost parentheses
13735/84/(19.75)/2.5 = 13735/84/19.75/2.5
= (13735)/(8419.75*2.5)
= 4795/4155

Therefore, (6,6-3 3/14)*5 5/6/(21-1,25)/2.5 = 4795/4155.