Advanced Web Construction - Head First HTML and CSS - page 434

So now that you understand widths, what's the total width
of the elixirs box? To start with, we know the content area
is 200 pixels. We've also set some left and right padding
that affects the width, as well as a border that's set to “thin”.
Just assume a thin border is 1 pixel thick, like it is on most
browsers. And what about margins? We set a left margin
value, but no right margin value, so the right margin is 0
pixels by default.
Here are all the properties that relate to width. Your job is to
figure out the total width of the elixirs <div>.
border-width: thin;
width: 200px;
padding-right: 20px;
padding-left: 20px;
margin-left: 20px;