Based on the clue 'age range of an octogenarian', what is the answer?

Based on the clue 'agatha christies mysteries solved by this detectiv...', what is the answer? Based on the clue 'agatha mary clarissa miller used this married name...', what is the answer? What is associated with: age 87 at his death in 1864 he was the oldest man ever to serve as chief justice of the us? Based on the clue 'age of a sophomore horse its also the usual age of...', what is the answer? What is referred to by 'ageless wonderwilde picturescom'? What is referred to by 'agenda fairground fanfair'? What is referred to by 'agent 99'? Based on the clue 'agent k agent j jack jeebs', what is the answer?