There are 30 x 2 = <<30*2=60>>60 attendees from company B.
Company C has 30 + 10 = <<30+10=40>>40 attendees.
Company D has 40 - 5 = <<40-5=35>>35 registered attendees.
So, the total attendees from company A, B, C, and D is 30 + 60 + 40 + 35 = <<30+60+40+35=165>>165.
Therefore there are 185 - 165 = <<185-165=20>>20 attendees that are not from companies A, B, C, or D.
#### 20