Generated by SassMeister.com.

input.scss

.o-layout  {
    &-three-columns {
        width: 33.333%;
        float: left;
    }
}

.layout-potatos {
    &-three-columns {
        @extend .o-layout-three-columns;
    }
}

output.css

.o-layout-three-columns, .layout-potatos-three-columns {
  width: 33.333%;
  float: left;
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.32.12",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}