Generated by SassMeister.com.

SassMeister-input.scss

%placeholder {
  display: inline-block;
  &:hover{ color: darken(#FFFFFF, 10%); }  
}

.class-a {
  @extend %placeholder;
  color: #000000;
}

.class-b {
  @extend %placeholder;
  color: red;
}

@mixin mixin {
  display: inline-block;
  &:hover{ color: darken(#FFFFFF, 10%); }
}

.class-c {
  @include mixin;
  color: purple;
}

.class-d {
  @include mixin;
  color: orange;
}

SassMeister-output.css

.class-a, .class-b {
  display: inline-block;
}
.class-a:hover, .class-b:hover {
  color: #e6e6e6;
}

.class-a {
  color: #000000;
}

.class-b {
  color: red;
}

.class-c {
  display: inline-block;
  color: purple;
}
.class-c:hover {
  color: #e6e6e6;
}

.class-d {
  display: inline-block;
  color: orange;
}
.class-d:hover {
  color: #e6e6e6;
}