There are 7 regions in the Venn diagram above
Circle C contains all the Coke drinkers, which are of 4 types:
Circle C is made up of 4 regions d,e,f, and h
Those in region d drink Coke but do not drink beer or whiskey
Those in region e drink Coke and beer, but do not drink whiskey.
Those in region h drink Coke, beer, and whiskey.
Those in region g drink Coke and whiskey, but do not drink beer.
 
Circle B contains all the beer drinkers, which are of 4 types:
Circle B is made up of 4 regions e,f,h, and i
Those in region e drink beer and Coke, but do not drink whiskey.
Those in region f drink beer, but do not drink coke or whiskey.
Those in region h drink beer, Coke, and whiskey.
Those in region i drink beer and whiskey, but do not drink Coke.
 
Circle W contains all the whiskey drinkers, which are of 4 types:
Circle W is made up of 4 regions g,h,i, and j
Those in region g drink whishey and Coke, but do not drink beer.
Those in region h drink whiskey, Coke, and beer.
Those in region i drink whiskey and beer, but do not drink Coke.
Those in region j drink whiskey, but do not drink Coke or beer.
 
Let's start with this clue:

>>...1 who drinks whiskey does not drink Coke. how many are in the group?

I take this to mean nobody drinks both Coke and whiskey.  That
means there are nobody in regions g and h.  So we put 0's there







>>...100 drink coke and beer...<<
 
So all 100 go in e since there are 0 in the middle. So we replace
e by 100



>>...200 drink beer and whiskey...<<

So all 200 go in i since there are 0 in the middle. So we replace
i by 200



>>...400 drink coke...<<

Three of the regions of circle C have 100, 0 and 0 in them.
So we have already accounted for 100 of the Coke-drinkers,
so the remaining 300 coke-drinkers are in region d.  So we
replace d by 300:



>>...500 drink beer...<<

Three of the regions of circle B have 100, 0 and 200 in them.
So we have already accounted for 300 of the beer-drinkers,
so the remaining 200 beer-drinkers are in region f.  So we
replace f by 200:


 
>>...300 drink whiskey...<<

Three of the regions of circle W have 0, 0 and 200 in them.
So we have already accounted for 200 of the whiskey-drinkers,
so the remaining 100 whiskey-drinkers are in region j.  So we
replace j by 100:



Now we have all 7 regions filled with numbers, so
we add them up:

300+100+200+0+0+200+100 = 900

So there were 900 at the party.  What a party!

Edwin