Writing it out in a string of expressions you get this:
7x^2 + x + 9 - (3x^2 + 4x - 5). Now don't forget that that negative sign out in front of the second polynomial changes the signs inside that set of parenthesis. so it would actually be 7x^2+x+9-3x^2-4x+5. Now let's simplify. 4x^2-3x+14 is that answer. Now to do the rest of the subraction...4x^2-3x+14-(4x^2-3x). Again, the negative sign is going to change the signs inside the parenthesis giving us 4x^2-3x+14-4x^2+3x. The 4x^2 terms cancel out as do the 3x terms, leaving us only with the 14.
