This is an arithmetic progression.
The common difference is 8:
[tex]11-3=8,19-11=8,\ldots.[/tex]The equation will be derived from the arithmetic progression:
[tex]a_n=a+(n-1)d[/tex][tex]a_n=3+(n-1)\cdot8\Rightarrow a_n=3+8n-8\Rightarrow a_n=-5+8n_{}[/tex]To find the 24th element:
[tex]a_{24}=-5+8\cdot(24)\Rightarrow a_{24}=-5+192\Rightarrow a_{24}=187[/tex]