hiding my sub menu for main nav with css but it's hiding all sub navs

I’m hiding my main nav with my child theme css using .sub_menu { display: none !important; } (as per your instructions) but it’s hiding my sub menu for this page: http://justhost.insightpd.com/accelerator/how-we-help/

I need the sub to show on for this menu, but no matter what i try, i can’t get it to work.

Can you please help?

Thanks!