The picture shows a triangular island: Which expression shows the value of c?

You deposit $5000 each year into an account earning 3% interest compounded annually. how much will you have in the account in 30 years?

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

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?