Question 71263
Well, if your goal is to simplify this then it would be easier to factor and cancel.  But if you must multiply, then that's a lot more work. 
Factor and cancel.
{{{((2x^2-x-3)/(3x^2+7x+4))*((3x^2-11x-20)/(4x^2-9))}}} Factor the terms.
{{{((2x-3)(x+1)/(3x+4)(x+1))*((3x+4)(x-5)/(2x-3)(2x+3))}}} Cancel where appropriate to get:
{{{(x-5)/(2x+3)}}}