By the inclusion–exclusion principle, we obtain that "65+45-30=80" people drink either coffee or tea. So "100-80=20" people drink neither coffee nor tea.
So a)probability that there is either coffee or tea drinker is "\\frac{80}{100}=\\frac{4}{5}" and b)probability that there is neither coffee nor tea drinker is "\\frac{20}{100}=\\frac{1}{5}"
Answer: a)"\\frac{4}{5}" b)"\\frac{1}{5}"
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