[Diphenyl Oxalate]

Ну например...

<span style="color: green" id="correct">0</span> / <span style="color: red" id="incorrect">0</span><br>
<span id="task"></span>
<input type="text" id="answer">
<input type="button" value="Ответить" onclick="check()">
<script>
function gen() {
	var a = (Math.round(Math.random() * 7) + 2), b = (Math.round(Math.random() * 7) + 2);
	return [a + "x" + b + "=", a * b];
}
var current = gen();
document.getElementById("task").innerHTML = current[0];
function check() {
	++document.getElementById( +document.getElementById("answer").value == current[1] ? "correct" : "incorrect" ).innerHTML;
	current = gen();
	document.getElementById("task").innerHTML = current[0];
}
</script>