Take the code below,
<strong><a href="#">Link</a></strong>
It will make the link bold.
Now consider this next example, does exactly the same thing, but which is the one to use from a SEO and semantic point of view?
<a href="#"><strong>Link</strong></a>
There is nothing significant to choose between them.
You should only use these if you want a particular link to have stronger emphasis. If you just want bold links, then you should use
a { font-weight: bold; }in your stylesheet.