If you set up your code like this, it’ll work.
<body>
<p>Number1:<input data-bind="value:n1"></p>
<p>Number2:<input data-bind="value:n2"></p>
<p>Number3:<input data-bind="value:n3"></p>
<script src="https://stackoverflow.com/questions/15090015/knockout.js"></script>
<script>
function ViewModel() {
var self = this;
self.n1 = ko.observable(10);
self.n2 = ko.observable(10);
self.n3 = ko.observable(10);
}
ko.applyBindings(new ViewModel()); `
</script>
</body>