Find the minimum or maximum of g(x)=x^2+9x-36

Can someone answer this question? : )

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?

Which expression can be used to find the cost of .75 kilogram of cheese at the price of $6.40 per kilogram?