Generated by SassMeister.com.

SassMeister-input-HTML.html

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<style>
  .admin_page textarea {
  height: 200px;
}
  
</style>
<div class="admin_page">
  <div>
    <div class="form-group">
      <textarea class="form-control"></textarea>
    </div>
  </div>
</div>

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

.admin_page {
  textarea {
    height: 200px;
  }
}

SassMeister-output.css

.admin_page textarea {
  height: 200px;
}

SassMeister-rendered.html

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<style>
  .admin_page textarea {
  height: 200px;
}
  
</style>
<div class="admin_page">
  <div>
    <div class="form-group">
      <textarea class="form-control"></textarea>
    </div>
  </div>
</div>