You can see the effect of installing `multiply-by-seven`

by
evaluating the following sample. Place the cursor after the following
expression and type `C-x C-e`. The number 21 will appear in the
echo area.

(multiply-by-seven 3)

If you wish, you can read the documentation for the function by typing
`C-h f` (`describe-function`

) and then the name of the
function, `multiply-by-seven`

. When you do this, a
`*Help*` window will appear on your screen that says:

multiply-by-seven is a Lisp function. (multiply-by-seven NUMBER) Multiply NUMBER by seven.

(To return to a single window on your screen, type `C-x 1`.)