How do you find x if your adding a fraction

How do you use the elimination method for this question? explain, because i really want to understand!

The graph of a function f(x)=(x+2)(x-4). which describes all of the values for which the graph is negative and increasing? all real values of x where x< -2 all real values of x where -2

What are the measures of angles a, b, and c? show your work and explain your answers. 25 points