Myujth

if user input this field

<input class="form-control" type="date"
 name="tgl_selesai"
 value="<?php echo htmlentities($row_inq['tgl_selesai'],
 ENT_COMPAT, 'utf-8'); ?>"
 size="32"><br>

Then automaticly this field will be fill

<label>Status Inquiry:</label><br>
<label>
 <input type="radio" name="status" value="Closed"
 <?php
 if (!(strcmp(htmlentities($row_inq['status'], ENT_COMPAT, 'utf-8'), "Closed"))) 
 echo "checked="checked"";
 
 ?>> Closed
 <input type="radio" name="status" value="On Progres"
 <?php
 if (!(strcmp(htmlentities($row_inq['status'], ENT_COMPAT, 'utf-8'),"On Progres"))) 
 echo "checked="checked"";
 
 ?>> On Progres
</label>

if user input = closed

The extension mysql_fetch_assoc() returns for the current line an associative array pairing a column name with its value. You can check if a value is NULL (ie a column is not filled) with the function is_null().

This answer is based on the code you posted in a comment:

$query_inq = "SELECT * FROM inquiry";
$inq = mysql_query($query_inq, $koneksi) or die(mysql_error());
$row_inq = mysql_fetch_assoc($inq);
$totalRows_inq = mysql_num_rows($inq)

Below we store in a boolean variable if the status is closed:

// Status is closed if $row_inq['status'] equals "Closed" **OR**
// the date thgl_selesai is filled 
$isClosedStatus =
 strcmp(htmlentities($row_inq['status'], ENT_COMPAT, 'utf-8'), "Closed") == 0 ||
 is_null($row_inq['tgl_selesai']);

(I assumed it was the case if the status in the base is set as "Closed" OR if the date tgl_selesai is filled; if it is not the case, editing the code is not very difficult.)

Finally, our HTML becomes:

<label>Status Inquiry:</label><br>
<label>
 <input type="radio" name="status" value="Closed"
 <?php echo $isClodedStatus?"checked":"") ?>> Closed
 <input type="radio" name="status" value="On Progres"
 <?php echo $isClodedStatus?"":"checked") ?>> On Progres
</label>

As you can notice, using a variable makes the code above way easier to read.

Note: the official PHP manual says that mysql_fetch_assoc is deprecated in PHP 5.5.0, and it was removed in PHP 7.0.0. Instead, the MySQLi or PDO_MySQL extension should be used. Click on the link to read more about this issue.