How to change the Zen theme to a single sidebar layout? I'm using Zen (version 7.x-5.5) as a base theme.

The problem is that it's showing with 2 sidebars layout. I searched in the documentation but I didn't find a way to change it to 1 sidebar layout (with main content of course ).  

I changed the SCSS files in _responsive.scss, but nothing changed.  

Is there any way to make this work?
In page.tpl.php, at line 109 and line 110, delete the sidebar you don't want

In style.css change this class
.region-sidebar-second{
float:left;width:20%;margin-left:0%;margin-right:-20%
} 

to be
.region-sidebar-second{
float:left;width:20%;margin-left:0%;margin-right:-20%;display:none;//add a display:none
} 

and change .two-sidebars #content {
float: left;
width: 60%;
margin-left: 20%;
margin-right: -80%;
}

to be

.two-sidebars #content {
float: left;
width: 80%; //change 60% to 80%
margin-left: 20%;
margin-right: -80%;
}