how to fix Object of class Illuminate\Support\Collection could not be converted to int?

I want to retrieve the data that stores the total questions on a quiz, but when I loop using the result of the total question data that I got using the query below, the result shows Object of class Illuminate \ Support \ Collection could not be converted to int. does anyone know how to solve it?

Here is the error

Here is my code

 public function insertStdAnswer(Request $request,$id){
        $_num = DB::table('quiz')
                    ->select('question_total')
                    ->where('id', $id)
                    ->get();

        for($i = 0; $i <= $_num ; $i++){
            $quiz_id = $id;
            $user_id_std_quiz = Auth::id();
            $std_answer = $request->input('answer-'.$i);
            $nomor_quiz = $request->input('soal-'.$i);
            DB::insert('insert into studentquiz (`std_quiz_id`,`user_id_std_quiz`,`std_answer`,`nomor_quiz`) values(?,?,?,?)',
            [$quiz_id,$user_id_std_quiz,$std_answer, $nomor_quiz]);
        }