There are several ways to achieve the same.

$wanted = Posting::where('user_id', '=', $user_id)->whereHas('offers', function($offerQuery){
    $offerQuery->where('id', '=', $offer_id);
})->get();

You probably do some manipulation with the user

$user = User::find($user_id);
$wanted = $user->postings()->whereHas('offers', function($offerQuery){
    $offerQuery->where('id', '=', $offer_id);
})->get();

Or you inspect the offer

$offer= Offer::find($offer_id);
$wanted = $offer->postings()->where('user_id', '=', $user_id)->get();

Or you make @Firtzberg's last example into one query:

$wanted = $offer->where('offer_id', $offer_id)->postings()->where('user_id', '=', $user_id)->get();

I think, loading the images should work with ->with('images'):

$wanted = $offer->where('offer_id', $offer_id)->postings()->where('user_id', '=', $user_id)->with('images')->get();

Somehow, this forum doesn't let me edit the previous posts, so here goes the corrected version:

$wanted = Offer::where('offer_id', $offer_id)->postings()->where('user_id', '=', $user_id)->with('images')->get();

This is a useful thread! Can anyone run this same example using morphedbymany relationship between Offers and Postings? I believe it should look almost identical except that eloquent will know to query the morph tables and join results.