I'm trying to solve the problem below using CDF and kinda lost. Can someone show me how it is done?
What is the probability that I roll two dice and they add up to at most 9?
$F(x) = P(X <= x)$
$F(9) = P(X <= 9)$
Do I make some table or something? I'm really lost.
Let $X,Y$ denote the first and the 2nd rolls and let $S=X+Y$. Note that $$ \mathbb{P}[S \le 9] = 1 - \mathbb{P}[S=12] - \mathbb{P}[S=11] - \mathbb{P}[S=10] $$ Can you take it from here?