Language: C++

using System;

class main
{
    static void Main(string[] args)
    {
        string s = string.Empty;
        var n = int.Parse(Console.ReadLine());        
        while (n-- != 0)
        {
            s = Console.ReadLine();
            string[] s1 = s.Split(' ');
            double x1 = double.Parse(s1[0]);
            double x2 = double.Parse(s1[1]);
            double x3 = double.Parse(s1[2]);
            double y1 = double.Parse(s1[3]);
            double y2 = double.Parse(s1[4]);
            double y3 = double.Parse(s1[5]);
            double a = Math.Sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
            double b = Math.Sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3));
            double c = Math.Sqrt((x3 - x1) * (x3 - x1) + (y3 - y1) * (y3 - y1));
            double r = (a * b * c) / Math.Sqrt((a + b + c) * (-a + b + c) * (a - b + c) * (a + b - c));
            double x = (((x1 * x1 + y1 * y1) * (y2 - y3)) + ((x2 * x2 + y2 * y2) * (y3 - y1)) + ((x3 * x3 + y3 * y3) * (y1 - y2))) / ((x1 * (y2 - y3)) + (x2 * (y3 - y1)) + (x3 * (y1 - y2))) * 0.5;
            double y = (((x1 * x1 + y1 * y1) * (x2 - x3)) + ((x2 * x2 + y2 * y2) * (x3 - x1)) + ((x3 * x3 + y3 * y3) * (x1 - x2))) / ((y1 * (x2 - x3)) + (y2 * (x3 - x1)) + (y3 * (x1 - x2))) * 0.5;
            Console.WriteLine("{0:F3} {1:F3} {2:F3}", x, y, r);
        }
        Console.ReadKey();
    }
}

Compiler output:
a.cc:1:7: error: expected nested-name-specifier before 'System'
    1 | using System;
      |       ^~~~~~
a.cc:5:22: error: 'string' has not been declared
    5 |     static void Main(string[] args)
      |                      ^~~~~~
a.cc:5:31: error: expected ',' or '...' before 'args'
    5 |     static void Main(string[] args)
      |                               ^~~~
a.cc:29:2: error: expected ';' after class definition
   29 | }
      |  ^
      |  ;
a.cc: In static member function 'static void main::Main(int*)':
a.cc:7:9: error: 'string' was not declared in this scope
    7 |         string s = string.Empty;
      |         ^~~~~~
a.cc:8:9: error: 'var' was not declared in this scope
    8 |         var n = int.Parse(Console.ReadLine());
      |         ^~~
a.cc:9:16: error: 'n' was not declared in this scope
    9 |         while (n-- != 0)
      |                ^
a.cc:11:13: error: 's' was not declared in this scope
   11 |             s = Console.ReadLine();
      |             ^
a.cc:11:17: error: 'Console' was not declared in this scope
   11 |             s = Console.ReadLine();
      |                 ^~~~~~~
a.cc:12:20: error: expected primary-expression before ']' token
   12 |             string[] s1 = s.Split(' ');
      |                    ^
a.cc:13:25: error: expected primary-expression before 'double'
   13 |             double x1 = double.Parse(s1[0]);
      |                         ^~~~~~
a.cc:14:25: error: expected primary-expression before 'double'
   14 |             double x2 = double.Parse(s1[1]);
      |                         ^~~~~~
a.cc:15:25: error: expected primary-expression before 'double'
   15 |             double x3 = double.Parse(s1[2]);
      |                         ^~~~~~
a.cc:16:25: error: expected primary-expression before 'double'
   16 |             double y1 = double.Parse(s1[3]);
      |                         ^~~~~~
a.cc:17:25: error: expected primary-expression before 'double'
   17 |             double y2 = double.Parse(s1[4]);
      |                         ^~~~~~
a.cc:18:25: error: expected primary-expression before 'double'
   18 |             double y3 = double.Parse(s1[5]);
      |                         ^~~~~~
a.cc:19:24: error: 'Math' was not declared in this scope
   19 |             double a = Math.Sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
      |                        ^~~~
a.cc:27:9: error: 'Console' was not declared in this scope
   27 |         Console.ReadKey();
      |         ^~~~~~~