Let's simplify the expression step by step:

$85-17$ = 68
$85+17$ = 102
$5+17$ = 22

Now plug these values back into the expression:
$68\ast 102$/$22^2$

68 * 102 = 6936
22^2 = 484

6936/484 = 14.33

Therefore, $85-17$$85+17$/$5+17$^2 = 14.33