I have to make few coding blocks and I'm stuck at 3 of them. Sorry anticipated for my bad english. 

First of all as said in summary. I tried this, it shows the even digits but also shows a tons of "0". 

```
<?php

$n = 33421;
$m = "";

while ($n != 0) {
    if (($n % 2 == 0) && ($n / 10) != 0) {
        $temp = strval($n % 10);
        $m .= $temp;
    }
    $n = $n / 10;
}

echo $m;
?

```

And I have 2 other things to do but no clue how to get it done and hope can someone help.

![I don't really know how this is called in english](https://i.stack.imgur.com/NAn4U.png)

![A system of equations with real numbers](https://i.stack.imgur.com/eqDkJ.png)