Perform the indicated operations and, if possible, simplify.
(a) n(n + 1) (n + 2) / 2 ∙ 3 - (n + 1) (n + 2) / 2
(b) n(n + 1) (n + 2) (n + 3) / 2 ∙ 3 ∙ 4
(n + 1) (n + 2) (n + 3) / 2 ∙ 3
(c) x2 - 9 / x3 + 27 ∙ 5x2 - 15x + 45 / x2 - 2x - 3 + x2 + x / 4 + 2x