8. If not 9? I'm glad that I could help brainliest?
Answer: 29.0 years
Explanation:
Expression for rate law for first order kinetics is given by:

where,
k = rate constant
t = age of sample
a = let initial amount of the reactant
a - x = amount left after decay process
a) for completion of half life:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.


b) for decomposition of 80 % of reactant



The age of a suspected vintage wine that is 20 % as radioactive as a freshlybottled specimen is 29.0 years
Keeping in mind a total ignorance of both the health benefits of these teas, and the interaction between milk and antioxidants, I believe that it is possible that milk could hinder these benefits.
Tea is usually a hot beverage. Milk, when added to this beverage, would easily dissolve. When a solute (milk) dissolves in a solvent (tea), the chemical properties of the resulting solution can become quite distinct from both of the original substances. It seems possible that the same chemical properties of tea that make it healthy could be altered by the addition of milk.