igorzyden,
<head>
<title>Математические задания</title>
<meta charset="utf-8">
<style type="text/css">
body{
counter-reset: num 0;
}
.primer:before{
counter-increment: num ;
content: counter(num)'. ';}
</style>
</head>
<body>
<div class="primer">
<span class="num"></span> +
<span class="num"></span> =
<input type="number" class="plus" width="5">
<button type="button">Проверить</button>
<p class="result"></p>
</div>
</body>
<script>
const random = n => Math.round(Math.random() * n);
let block = document.querySelector('.primer');
let length = 99;
let arr = Array.from({length}, _ => block.cloneNode(true));
document.body.append(...arr);
document.querySelectorAll('.primer').forEach(div => {
let sum = 0;
div.querySelectorAll('.num').forEach(span => {
let num = random(10);
span.textContent = num;
sum += num;
})
let input = div.querySelector('.plus'),
button = div.querySelector('button'),
result = div.querySelector('.result');
button.addEventListener('click', _ => result.textContent = input.value == sum ? 'Правильно' : 'Неправильно')
})
</script>