Hi,
That line of htaccess says:
If the host is legacytravel.com OR www.legacytravel.com, then lets try this rule below.
One conditions will always be true since the htaccess is on your site. So they cancel each other out, and are not needed.
The rule says if the URI matches the regular expression '^carrollton-travel-agent$' then redirect (r=301) to the target URL and stop processing rules (L flag for last)
Your RewriteRule target doesn't need characters escaping because it is not a regular expression, just a URL to redirect to. You also don't need the quotes, they're useful for grouping arguments with spaces in them but that's not affecting it.
Really this rewriterule doesn't accomplish anything, it redirects /carrollton-travel-agent to /carrollton-travel-agent, forcing the www. no matter which version is accessed. But if that is what you're wishing to achieve then there's a much simpler solution:
RewriteCond %{HTTP_HOST} !^www.legacytravel.com$ [NC]
RewriteRule ^(.*)$ http://www.legacytravel.com/$1 [R=301,L]
Notice we only use the \backslash to escape characters in regex patterns, and not in our target URL. What that rule will do is redirect any visitor where the host is missing the www to the equivalent page with the preceding www.
Hope that helps.