How can I make my house numbers using Microsoft Works the 72 font isn't nearly large enough?

You're not limited to the font sizes MS Works gives you !

Open the Word-processing part of the suite.

Type your house number.

Highlight the whole number (so it shows white text on a black background).

Now - instead of using the drop-down arrow to the right of the point figure - type a point size into the box.

You can theoretically type any number for the point size - you're only limited by the size of paper your printer is capable of using. For a two-digit number, in Times New Roman font - a point size of 425 is possible for an A4 sheet of paper !