Question 147139
To answer this question, first assign a variable for the probability of not playing.  How about x?  Given that the probability of not playing is x, then the probability of playing would be 9 times x, or 9x (this is given in the question).  The sum of both probabilities is 1, so given this information, you can make an equation and solve.  {{{9x + x = 1}}}  Combine like terms and get {{{10x=1}}}.  Then to isolate the variable, divide both sides by 10 and get {{{x=1/10}}}.  There, you have the variable!  But do not stop there!  x represents the probability of not playing, but we want the probability of playing, right?  Since the probability of playing is 9x, plug in 1/10 for x.  Your expression should look like {{{9(1/10)}}}.  Your answer should be 9/10 because it is {{{9/1 x 1/10}}}. So 9/10 is the probability that San Francisco plays in the next Super Bowl.