<input type="number" id="a">
<input type="number" id="b">
<button onclick="calc()">Hesabla</button>
<p id="result"></p>
<script>
function calc(){
let a = Number(document.getElementById("a").value);
let b = Number(document.getElementById("b").value);
document.getElementById("result").innerHTML = a + b;
}
</script>