We are told the sequence is arithmetic. This means that the difference between one therm and the next is a constant.
We are also given two terms of the sequence. Let's see what their difference is
[tex]a_{11}-a_7=94-58=36[/tex]This means that, in general
[tex]a_{k+4}-a_k=36[/tex]With this, we can deduce that the difference between any two cnsecutive terms will be 9, for example
[tex]a_7=58,a_6=49,a_5=40,a_4=31,a_3=22[/tex]Indeed,
[tex]a_7-a_3=58-22=36[/tex]Now we should find the first term of the sequence, a₀, in order to find the rule for the nth term.
[tex]a_2=13,a_1=4,a_0=-5[/tex]In general, the rule for the nth term of an arithmetic sequence is given by
[tex]a_n=a_0+d(n)[/tex]where d is the difference between two consecutive term. In this case we have
[tex]a_n=-5+9\cdot n[/tex]with n=0,1,2,....
