The average price of gas is 1.85 per gallon. Assume that each week it goes up 5 cents with probability 40% or down 5 cents with probability 60%. Find the probability that the average price per gallon goes down to 1 before it comes back to 2.
I have the answer to this problem and I know this is a two sided asymmetric case with $a=20$, $b=40$, $p=.4$, and $q=.6$. What I do not understand is how $x=37$. Can someone explain how it comes out to that using Wald's Identity?