How do i use substr on 2 divs?

How can i do so numb's last 2 numbers randoms like "text's" last 2? I can't do it with, document.write(str.substr(-2)); beacause its two divs..

How do i do?

<div id="numb">72-450 04 <script type="text/javascript">
document.write(Math.floor(Math.random()*9开发者_运维技巧0) +10);
</script></div>


<div id="text">
49</div>

If I understand correctly you want to print the same random number as las two chars of "#numb" div and text div. For that you can try this:

<script type="text/javascript"> 
        var lastNumber = Math.floor(Math.random()*90) +10; 
    </script>
    <div id="numb">72-450 04 <script type="text/javascript"> document.write(lastNumber); </script></div>  
    <div id="text"> <script type="text/javascript"> document.write(lastNumber); </script></div>