1. The problem statement, all variables and given/known data 2. Relevant equations Σ(n*2/5*(3/5)^(n-1)=5/2 3. The attempt at a solution First I found the number of tosses needed to get heads, but I don't understand how to interpret this in the E[X] formula. I know that my p(x)=.40 what is my x ? "tails for the first time" ? how to translate it in a numerical representation ? and the summation is from n=0 to n=2.5 ?? Thanks, Roni.