1. ## Probability_2

2. Originally Posted by kochwow
Those are completely straightforward problems.
So where are you having difficulties?
Do you know the rules and/or the definitions involved?

3. Originally Posted by Plato
Those are completely straightforward problems.
So where are you having difficulties?
Do you know the rules and/or the definitions involved?
I'm sure that for you they are completely straightforward and you do not have any problems with solving them. However, I posted it, simply because I don't understand it at all. What would be the point of posting thread which I can solve?
I don't know the rules, probability it's just one of those things that don't come into my head and I can't understand them...

I'm sorry if I've disappointed you by NOT KNOWING the answer for this completly straightforward problem.

You tell us what are the correct formulas (rules) for $\displaystyle P(A|B) = ?\;\& \;P(A \cup B) = ?$
$\displaystyle \left( {A^c \cap B^c } \right) = \left( {A \cup B} \right)^c \; \Rightarrow \;P\left( {A^c \cap B^c } \right) = 1 - P\left( {A \cup B} \right)$.