1-1-3 app/Http/Controllers/TopicController.php

<?php

namespace App\Http\Controllers;

use App\Topic;
use Illuminate\Http\Request;

class TopicController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        //
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        //
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        $topic = Topic::create($request->all());
        return redirect()->route('exam.show', $topic->exam_id);
    }

    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        //
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit(Topic $topic)
    {
        $exam = $topic->exam;
        return view('exam.show', compact('exam', 'topic'));
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, Topic $topic)
    {
        $topic->update($request->all());
        return redirect()->route('exam.show', $topic->exam_id);
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy(Topic $topic)
    {
        $topic->delete();
        return redirect()->route('exam.show', $topic->exam_id);
    }
}