ANSWER
The recursive formula is
[tex]a_n = a_ {n - 1}+ 4[/tex]
EXPLANATION
The given sequence is 12,16,20,24,28
The first term of this sequence is
[tex]a_1=12[/tex]
The common difference is
d=16-12
d=4
The recursive formula is given by
[tex]a_n = a_ {n - 1}+ d[/tex]
So we need to substitute the known values to get
[tex]a_n = a_ {n - 1}+ 4[/tex]