#5n^2 - 3n - 2 + (-7n^2 + n + 2), " Adding first two terms"#
#=>5n^2 - 3n - 2 - 7n^2 + n + 2, " removing bracket"#
#=>5n^2 - 7n^2 - 3n + n - cancel 2 + cancel 2, " rearranging like terms together"#
#=>-2n^2 -2n#
#-2n^2 - 2n - (12n^2 -n + 9, " subtracting the tnird term from the result"#
#=> - 2n^2 - 2n - 12n^2 + n - 9, " removing bracket"#
#=> -2n^2 - 12n^2 - 2n + n - 9, " rearranging terms"#
#color(brown)(=> -14n^2 -n - 9#