JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="autoban_euro" name="autoban_euro">
<br/>
<input type="text" id="autoban2_euro" name="autoban2_euro">
<br/>
<input type="text" id="autoban3_euro" name="autoban3_eruo">
<br/>
<input type="text" id="kurs" name="kurs">
<br/>
<input type="text" id="hgs_izrazhodeno" name="hgs_izrazhodeno">
<br/>

JavaScript

$(document).ready(function () {
    $('#autoban_euro, #autoban2_euro, #autoban3_euro, #hgs_izrazhodeno').keyup(function () {
        var a = $("#autoban_euro").val();
        var b = $("#autoban2_euro").val();
        var d = $("#autoban3_euro").val();
        var e = $("#kurs").val();
        var c = (parseInt(a) + parseInt(b) + parseInt(d)) / parseInt(e);
        $("input[name=hgs_izrazhodeno]").val(c);
    });
});