A - the sum of two dice is 7
B - the first die is 2
[tex] P(A|B)=\dfrac{P(A \cap B)}{P(B)}\\\\
|\Omega|=6^2=36\\
|A\cap B|=1\\
|B|=1\cdot6=6\\\\
P(A\cap B)=\dfrac{1}{36}\\
P(B)=\dfrac{6}{36}=\dfrac{1}{6}\\\\
P(A|B)=\dfrac{\dfrac{1}{36}}{\dfrac{1}{6}}=\dfrac{1}{36}\cdot6=\dfrac{1}{6} [/tex]
