A number line is this:

------------------------------------------
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7

This:



means you are to darken the part between -3 and 5
EXcluding 3 (because of the <) but INcluding 5 
(because of the <. To show that you EXclude
the -3, you put an open circle there. To indicate
that you INclude the 5, you put a darkened circle 
there, like this:

----------o=======================•--------
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7

That's all there is to it.  Some textbooks use a parenthesis to
show exclusion and a bracket to show inclusion.  If you have one
of those books, then you should write it this way:

----------(=======================]--------
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7

This way is a little better because it gets you ready to
learn about interval notation, which is just an abbreviation
for that number line graph above.  That abbreviation is this:

        (-3,5]

Edwin