The expression is, .
(Apply additive inverse property: )
(Apply additive identity property: )
The sum is 6.
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
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.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=9585e41b9a890e9db984ddadfad77e1e.png\")
(Apply additive inverse property: ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=f9007cb31aae82c6e5cb950ed42ad7cd.png\")
)![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b2d202faac0f2658fd141425a56f8983.png\")
(Apply additive identity property: ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c628a15b880a08a5f3db5704033f7cb3.png\")
) ![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")