using System;

using System.Linq;

​

class Alquiler

{

    public Cargo[] Cargos

    {

        get;

        set;

    }

}

​

class Cargo

{

    public int id

    {

        get;

        set;

    }

}

​

public class Program

{

    public static void Main()

    {

        var alquileres = new[]{new Alquiler()

        {Cargos = new[]{new Cargo()

        {id = 1}, new Cargo()

        {id = 2}}}, new Alquiler()

        {Cargos = new[]{new Cargo()

        {id = 2}, new Cargo()

        {id = 3}}}};

        var allCargos = alquileres.SelectMany(s => s.Cargos).Where(s => s.id == 2);

        Console.WriteLine(allCargos.Count());

    }

}