Generated by SassMeister.com.

SassMeister-input-HTML.jade

.row
  .c-6
    h1 hello world
    .row
      .c-4
        h1 inside
      .c-6.c-last
        h1 right
  .c-6.c-last 
    h1 second hello

SassMeister-input.scss

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// Juice (v1.0.0)
// Susy (v2.2.2)
// ----

@import "juice";
@import "susy";


$col-nums: 12;
$susy: (
  columns: $col-nums,
  gutters: 1/4,
  container: 90%
);
.row {
 @include clearfix();  
}
@for $i from 1 through $col-nums {
  .c-#{$i} {
     @include span($i);
  }
}
.c-last {
  float: right;
  margin-right: 0;
}

SassMeister-output.css

.row {
  *zoom: 1;
}
.row:before, .row:after {
  display: table;
  content: '';
  line-height: 0;
}
.row:after {
  clear: both;
}

.c-1 {
  width: 6.77966%;
  float: left;
  margin-right: 1.69492%;
}

.c-2 {
  width: 15.25424%;
  float: left;
  margin-right: 1.69492%;
}

.c-3 {
  width: 23.72881%;
  float: left;
  margin-right: 1.69492%;
}

.c-4 {
  width: 32.20339%;
  float: left;
  margin-right: 1.69492%;
}

.c-5 {
  width: 40.67797%;
  float: left;
  margin-right: 1.69492%;
}

.c-6 {
  width: 49.15254%;
  float: left;
  margin-right: 1.69492%;
}

.c-7 {
  width: 57.62712%;
  float: left;
  margin-right: 1.69492%;
}

.c-8 {
  width: 66.10169%;
  float: left;
  margin-right: 1.69492%;
}

.c-9 {
  width: 74.57627%;
  float: left;
  margin-right: 1.69492%;
}

.c-10 {
  width: 83.05085%;
  float: left;
  margin-right: 1.69492%;
}

.c-11 {
  width: 91.52542%;
  float: left;
  margin-right: 1.69492%;
}

.c-12 {
  width: 100%;
  float: left;
  margin-left: 0;
  margin-right: 0;
}

.c-last {
  float: right;
  margin-right: 0;
}

SassMeister-rendered.html

<div class="row">
  <div class="c-6">
    <h1>hello world</h1>
    <div class="row">
      <div class="c-4">
        <h1>inside</h1>
      </div>
      <div class="c-6 c-last">
        <h1>right</h1>
      </div>
    </div>
  </div>
  <div class="c-6 c-last">
    <h1>second hello</h1>
  </div>
</div>