DB_app/app/Empoyees_inf.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Empoyees_inf extends Model
{
    public function sold_products() {
        return $this->belongTo(Sold_products::class, 'customer_id', 'id');
    }

    public function duties()
    {
        return $this->belongsToMany(Employees_dutie::class, 'duties', 'emp_id', 'duty_id');
    }
}