The idea is to get the unknown alone in the middle for adding the same thing
to ALL THREE sides, and sometimes multiplying ALL THREE SIDES by the same
quantity. 

                                -2 < a + 3 < 8

Add -3 to ALL THREE SIDES:

                                -2 < a + 3 < 8
                                -3      -3  -3
                               ———————————————— 
                                -5 < a     < 5

So the solution is -5 < a < 5

Graphed on a number line it looks like this:
-------n============================o------
-7 -6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6  7 
  
There is a closed circle "n"at -5 and an open circle "o"at +5.
The reason is because -5 is included with the shaded part,
but +5 is excluded.  That's because the -5 had the symbol
"<" next to it whereas the +5 had the symbol "<" next
to it.  

Interval notation is an abbreviation for the graph above, where
a bracket denotes a closed circle and a parenthesis denotes an
open circle, and the endpoints of the shaded interval are in
between separated by a comma.  The above graph would be 
abbreviated with interval notation as

 [-5, 5) 

Edwin