(2x-7))6x+9)

your brackets don't match, the number of left and right brackets should be equal.

did you mean
(((2x-7))6x+9) ?
then
12x^2 - 42x + 9 is your final expression.

(2x-7)(6x+9)

12x^2+18x-42x-63
12x^2-24x-63

It seems like the expression you provided is incomplete or may contain some errors. In order to simplify or evaluate an expression, it needs to be properly formatted with all the necessary operators and parentheses. Please double-check the expression and ensure that it accurately represents the expression you want to simplify or evaluate.