Hi could any one help me with the following question please.

A poll is carried out in the run up to a general election which give the following results:

Age Group---Conservatives---Labour---Liberal Democrats---Others

18-34--------32.7%----------30.7%-----------29.0%------7.6%

35-64--------35.5%----------28.9%-----------24.8%------10.8%

65+ ---------43.9%----------31.0%-----------16.0%------9.1%

The age groups represented are:

18-34-------35-64------65+

21.9%-------54.1%-----24.0%

(a) Find the probability that a randomly chosen voter who takes part in the poll but whose age is not know voted Conservative.

(b) Suppose the voter did vote Conservative, find the probability that he/she is at least 65 years old.

I think for (b) you would use the conditional probability formula but how would (a) be calculated?