.inner-content {
    width: 755px;
    position: relative;
}

<script>
    function calculate()
    {
        a=document.getElementById('pole1');
        b=document.getElementById('in');
        result=Number(a.value)+100500;
        b.textContent=result;
    }
</script>

<form method="POST" id="form">
<select id="pole1" onchange="calculate()" >
            <option value='0'>число</option>
            <option value='3'>3</option>
            <option value='5'>5</option>
            <option value='10'>10</option>
            <option value='15'>15</option>
            <option value='20'>20</option>
</select>
</form>
Итоговая цена: <span id="in"></span>

UPDATE  таблица SET link = REPLACE(link, '.html', '.htm') WHERE ID = 100;