There is a city that is for all intents and purposes 100% dominated by two cab companies: the Yellow Cab Company and the White Cab Company, and their cabs are colored accordingly. The former is the dominant taxi company. Yellow cabs number 81% of the market. You took a taxi and realized that you left your smartphone in it moments after it pulled away, turning at a corner and going out of site. You cannot remember the color of the cab, so you call both companies. They both deny having found a smartphone, but you are certain that you left it in the taxi. It was a very bright day. You lean heavily toward thinking it was a white cab. After all, there are so many yellow cabs on the road, and you remember yours as being somehow distinctive. You are almost sure it was white, like 90% sure. Now, employ Bayes's Rule to figure out the probability that the cab was white given the degree to which you believe it was. Let's assign variables thusly(you may not need to use all the variables): Y = The taxi was yellow. W = The taxi was white. T = You think the taxi was white.

Now, what would the equation look like?