It's simple addition in Javascript. But I don't understand why result is 1510 instead of 15+10.

```
<script>
function doCalc(){
    with (document.calc){
    sum1.value = orderin.value+ ordercheck.value
    }
}
</script>
<form method="post" name="calc" enctype="multipart/form-data">

    <input checked="checked" value="0" name="orderin" type="RADIO" onChange="doCalc()">+0
    <input value="15" name="orderin" type="RADIO" onChange="doCalc()">+15
    <br><br>
    <input id="ordercheck1" checked="checked" value="0" name="ordercheck" type="RADIO" onChange="doCalc()">+0
    <input id="ordercheck2" value="10" name="ordercheck" type="RADIO" onChange="doCalc()">+10
    <br><br>
    TOTAL: <input size="7" value="0" name="sum1" readonly="readonly" border="0">
    <input onClick="doCalc()" value="TOTAL" name="button" type="button">
</form>

```