This class can compare two comma separated word lists and return the matching percentage.

FindWorkPercentage.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WordCompare
{
    class FindWorkPercentage
    {
        static void Main(string[] args)
        {
            FindWorkPercentage pr = new FindWorkPercentage();
            Console.WriteLine(pr.GetPercentage("cat, cat, dog, puppy", "cat, bite, bark"));
            Console.ReadKey();
        }

        public float GetPercentage(string firstInputs, string secondInputs)
        {
            float total = 0f;
            float count = 0f;
            float result = 0f;

            //Removing Spaces
            firstInputs = firstInputs.Replace(" ", "");
            secondInputs =  secondInputs.Replace(" ", "");
                    
            string[] firstArray = firstInputs.Split(',');
            string[] secondArray = secondInputs.Split(',');

            total = firstArray.Length + secondArray.Length;

            for (int i = 0; i < firstArray.Length; i++)
            {
                for (int j = 0; j < secondArray.Length; j++)
                {
                    if (firstArray[i] == secondArray[j])
                    {
                        count++;
                        break;
                    }
                }
            }

            for (int i1 = 0; i1 < secondArray.Length; i1++)
            {
                for (int j1 = 0; j1 < firstArray.Length; j1++)
                {
                    if (secondArray[i1] == firstArray[j1])
                    {
                        count++;
                        break;
                    }
                }
            }

            //Caculating result as percentage
            result = count / total * 100;     
 
            /*
             * To have result as a ratio uncomment below line and comment above line.
             * 
             * Note : Nothing ;)
             */
            //result = count / total;

            return result;
        }
    }
}