(2n - 9) - 5(-2.4n + 4) =
The first set of parentheses is unnecessary, so we just drop them.
= 2n - 9 - 5(-2.4n + 4)
Now we distribute -5 by the second set of parentheses. Each term in the parentehses is multiplied by -5.
= 2n - 9 + 12n - 20
Now we combine like terms.
= 2n + 12n - 9 - 20
= 14n - 29