Answer
See below.
Work Step by Step
Using the example
$7-(-9)-8+4+(1)+(-1)=$...
the lines starting with "..." give instructions on how to simplify.
... First, write any subtraction as an addition of the additive opposite number,
$=7+9+(-8)+4+(1)+(-1) $
... Add all the positive numbers,
$=(7+9+4+1)+(-8)+(-1) $
$=21+(-8)+(-1) $
... Add all the negative numbers
$=21-9$
... Use the rule for adding numbers of opposite signs
$=12$
