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Program returning values as NaN

Im trying to get this program to work and i have everything running, but my values return as NaN. I've tried initializing the variables as numbers both in and outside the function to no avail. Any help?

EDIT: added in the entire script, html and all incase it helps alongside the edits suggested thus far.

<html>
<head>

   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width,initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
   <title>Placeholder</title>


</head>

<body>
    <header>
        <h1>Resturant Calculator</h1>
    </header>

    <article>
        <fieldset>
                <label for="bill">
                    Bill Amount
                </label>
                <input type="number" id="bill" />
        </fieldset>
        <fieldset>
                <label for="tip">
                    Tip Percent
                </label>
                <input type="number" id="tip" />
                <label>(enter as whole number)</label>
        </fieldset>
        <fieldset>
                <label for="peeps">
                    # of people
                </label>
                <input type="number" id="peeps" />
        </fieldset>
        <button id="submit" onclcick="calculate()">Calculate</button>
        <p id="tipAmount">Tip Amount:</p>

        <p id="total">Total Bill:</p>
        <p id="totalByPeep">Total per Person:</p>
    </article>

   <script>
        "use strict"
        var bill = document.getElementById("bill").value;
        var tip = document.getElementById("tip").value;
        var peeps = document.getElementById("peeps").value;

        var total;
        var totalTip;
        var tpPerson;

        function calculate(){
            totalTip = bill.value / (tip.value * 0.01);
            total = bill.value + totalTip;
            tpPerson = total / peeps.value;

            document.getElementById("tipAmount").innerHTML = "Tip Amount: " + totalTip;
            document.getElementById("total").innerHTML = "Total: " + total;
            document.getElementById("totalByPeep").innerHTML = "Total per Person: " + tpPerson;
        }


        function createEventListener(){
            var submitButton = document.getElementById("submit");

            if (submitButton.addEventListener){
                submitButton.addEventListener("click", calculate, false);
            }
            else if(submitButton.attachEvent){
                submitButton.attachEvent("onclick", calculate);
            }

        }

        if (window.addEventListener){
            window.addEventListener("load", createEventListener, false);
        }
        else if (window.attachEvent){
            window.attachEvent("onload", createEventListener);
        }
</script>
   </script>

</body>
</html>

You need to get the values from the elements bill , tip , peeps Probably something like document.getElementById("bill").value

Using just document.getElementById("bill") you are selecting the element, but not its value

You need to read the value inside calculate()

    function calculate(){
        bill = +bill.value, tip = +tip.value, peeps = +peeps.value;
        totalTip = bill/ (tip * 0.01);
        total = bill + totalTip;
        tpPerson = total / peeps;

        document.getElementById("tipAmount").innerHTML = "Tip Amount: " + totalTip;
        document.getElementById("total").innerHTML = "Total: " + total;
        document.getElementById("totalByPeep").innerHTML = "Total per Person: " + +tpPerson;
    }

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