Morris,
<!DOCTYPE html>
<html>
<head>
<title>Селекты</title>
<meta charset="utf-8">
<style type="text/css">
label {
display: table-row;
}
</style>
</head>
<script type="text/javascript">
function calculat(obj) {
var num = document.querySelectorAll('[name^="Number"]')[qr2.value].value;
obj.res1578.value = num.replace(/,/, ".");
obj.res2.value = obj.r1.value;
}
</script>
<form>
<select id="qr2">
<option value="0"selected>10</option>
<option value="1">12</option>
<option value="2">14</option>
<option value="3">16</option>
</select>
<input type="text" style="width:55px" id="res1578">
<label>10<input type="text" value="1.9" style="width:26px" name="Number55"></label>
<label>12<input type="text" value="1.4" style="width:26px" name="Number56"></label>
<label>14<input type="text" value="1.56" style="width:26px" name="Number57"></label>
<label>16<input type="text" value="0.98" style="width:26px" name="Number58"></label>
<select id="r1">
<option value="10">0.1</option>
<option value="2">0.5</option>
<option value="1">1</option>
</select>
<input type="text" style="width:55px" id="res2">
<br><br>
<input type="button" name="WB" value="Ok" onclick="calculat(form)">
</form>
</html>