auto-fit

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>use-auto-fill-and-auto-fit-if-the-number-of-repeated-grid-tracks-is-not-to-be-def</title>
    <style>
        .container > * {
            background-color: hotpink;
        }

        .container {
            display: grid;
            grid-gap: 10px;
            height: 100vh;
            grid-template-columns:
                    repeat(
                            auto-fit,
                            minmax(50px, auto)
                            minmax(70px, auto)
                            minmax(90px, auto)
                    );
        }
    </style>
</head>
<body>
<div class="container">
    <div class="box a">A</div>
    <div class="box b">B</div>
    <div class="box c">C</div>
</div>
</body>
</html>

// Code goes here

/* Styles go here */