<div class="vertical-navbar-padding">calculator</div>
        <ul>
            <li><a data-strona="#evolves-calculator">calc</a></li>
        </ul>

    <section>
        <div id="evolves-calculator" style="display: none;">
            <form class="form-calculator" action="" method="post">
                some input<input id="dd" type="text"/>
                some input<input id="dd" type="text"/>
                <input onclick="calculator()" type="submit" value="Submit">
            </form>
        </div>
    </section>

<script>
    $(function () {
        $("a").click(function () {
            var selektor = $(this).data('strona');
            $('section div').css('display', 'none');
            $(selektor).css('display', 'block');
        });
    });
    function calculator() {
        alert("some text");
        var variable = document.getElementById("evolves-calculator");
        $(variable).css('display', 'block');
    }
</script>