3.2

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
namespace CSharpLight
{
    public static class Program
    {
        public static void Main()
        {
            int maxValue = int.MinValue;
            int[,] matrix = new int[10, 10];
            Random random = new Random();

            for (int i = 0; i < matrix.GetLength(0); i++)
            {
                for (int j = 0; j < matrix.GetLength(1); j++)
                {
                    matrix[i, j] = random.Next(0, 31);
                    Console.Write(matrix[i, j] + " ");
                    if (matrix[i, j] > maxValue)
                    {
                        maxValue = matrix[i, j];
                    }
                }
                Console.WriteLine();
            }
            Console.WriteLine("\n" + maxValue + "\n");

            for (int i = 0; i < matrix.GetLength(0); i++)
            {
                for (int j = 0; j < matrix.GetLength(1); j++)
                {
                    if (matrix[i, j] == maxValue)
                    {
                        matrix[i,j] = 0;
                    }
                    Console.Write(matrix[i, j] + " ");
                }
                Console.WriteLine();
            }
        }
    }
}