using System;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            [

              {

                ""bpm"": ""766"",

                ""time"": ""20:14:57"",

                ""confidence"": ""0""

              },

              {

                ""bpm"": ""766"",

                ""time"": ""20:14:57"",

                ""confidence"": ""0""

              },

              {

                ""bpm"": ""767"",

                ""time"": ""20:14:33"",

                ""confidence"": ""0""

              }

            ]";

        var array = JArray.Parse(json);

        var obj = array.SelectToken("$.[?(@.bpm=='767' && @.time=='20:14:33')]");

        Console.WriteLine(obj != null ? obj.ToString() : "(null)");

    }

}