$Given \ Series : \\ 3 \ 9 \ 18 \ 35 \ 58 \\Difference \ b/w \ each \ successive \ number \ in \ the \ series \ : \\ 6 \ 9 \ 17 \ 23 \\Difference \ in \ this \ series : \ 3 \ 8 \ 6 \ \cdot \cdot \\therefore \ next \ term \Rightarrow 16 \\Answer \ as \ follows \Rightarrow (6,9,17,23,(23+16) \ 39) \\ \Rightarrow (3,9,18,35,58,(58+39) \ 97)\!$