Parent Theme wins CSS Specifity over Child

Hello I am using bp-social-child

I add the following lines to the child-style.css
#box-left{width:26%;}
#box-center{width:70%;}

When I look at the page, the new styles are not being respected by the theme. I look in Firebug, they are being read but the BP-Social parent theme is being given the specificity over the child theme.

If I use Firebug to disallow the parent stye, the page renders as I intended

I thought it was supposed to be the other way around, use the child theme and make changes in the _inc style to make changes. This way you will not lose them in the event of an upgrade.

I can of course add !importance but would rather find out the proper way to do this.

I have a snipping of the Firebug Dev Panel if you need it