How to include a variable in a laravel redirect

I have a variable in a Laravel 5 controller which I am trying to include in the url of a redirect link, however nothing I've tried seems to work, my code is currently as follows.

$newChallenge = ((int) request('challenge_id') + 2);

return redirect('/texttext/');

However, this doesn't use the variable represented by $newChallenge, but rather
"" as a string, how should this be done?

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