First, let’s start things off by centering things up a bit.

h2 {
  text-align: center;
}
table {
  text-align: center;
}

Notice this centers the h2s on the page, but leaves the tables off to the side, where they sit by default. If we look closely, however, we can see that the text in the table cells is now centered. The 7, for example, sits centered atop the 14. We’ll need something else to center them across the page.