index.html

<!DOCTYPE html>
<html lang="pt-br">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CHURRASCÔMETRO</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>
    
    <div class="container">

        <h1>Churrascômetro</h1>

        <input type="number" id="adult" name="adult" placeholder="N° de Adultos">
        <input type="number" id="children" name="children" placeholder="N° de Crianças" >
        <input type="number" id="duration" name="duration" placeholder="Duração (em horas)">

        <div>
            <div class="buttonArea">

                <button onclick="calculate()">
                    Calcular
                </button>

            </div>

            <div id="result" class="result">

            </div>

        </div>
    <script src="script.js"></script>
</body>
</html>