Question 1165946

 =======   S    N   T
White (W) 299 508 807 
Black (B).   47 146 193 
Column Total 346 654 1,000 
P(S)=346/1000 or 0.346
P (W)=0.807 
Both of these look directly at the totals for the row or column.
P(S|W)  There are 807 W and 299 smoke so the answer is 299/807, or 0.371
P(S|B)  is 47/193 or 0.244
P(S and W) is one of the inner cells. S and W is 299 and the denominator is 1000, so answer is 0.299
P (N and B) is 146/1000 or 0.146