help I dont know what to do

@content;

Adding the preceding line to your mixin allows you pass content from where you use your mixins to the actual mixin itself.

Here is the documentation from the SASS documentation page (http://sass-lang.com/documentation/file.SASS_REFERENCE.html):

Passing Content Blocks to a Mixin

It is possible to pass a block of styles to the mixin for placement within the styles included by the mixin. The styles will appear at the location of any @content directives found within the mixin. This makes it possible to define abstractions relating to the construction of selectors and directives.

For example:

@mixin apply-to-ie6-only {
  * html {
    @content;
  }
}
@include apply-to-ie6-only {
  #logo {
    background-image: url(/logo.gif);
  }
}

Generates:

* html #logo {
  background-image: url(/logo.gif);
}

The same mixins can be done in the .sass shorthand syntax:

=apply-to-ie6-only
  * html
    @content

+apply-to-ie6-only
  #logo
    background-image: url(/logo.gif)

Note: when the @content directive is specified more than once or in a loop, the style block will be duplicated with each invocation.

(```) $btn-background: #dc143c;

/* Write your SCSS code below. */

@mixin button { @content; font-size: 1.25em; background-color: $btn-background; } a { @include button; } (```)