First, let's solve the inner parentheses first:

72$20,74:6,8-7,6:19$ = 72$20.74/6.8-7.6/19$ = 72$3.04411765-0.4$ = 722.64411765
= 190.1029416

Now, let's plug this value back into the outer parentheses:

$25,8-3,190.1029416$0.5
= $22.8-95.05168$0.5
= $-72.25168$*0.5
= -36.12584

Therefore, the final answer is -36.12584.