28800000, 1440000, 72000, 3600, 180, ...

Which representation has a constant of variation of -2.5

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?

Solve the formula ax+ by = c for x.