x
<html><body><form action="/action_page.php" method="get"oninput="x.value=parseInt(a.value)+parseInt(b.value)">0<input type="range" id="a" name="a" value="50">100 +<input type="number" id="b" name="b" value="50">=<output name="x" for="a b"></output><input type="submit"></form></body></html>