Answer:
[tex]9th=31[/tex]
Step-by-step explanation:
From the question we are told that:
Seventh term [tex]7th= 21[/tex]
Common difference [tex]d= 5[/tex]
Generally Equation for seventh term
[tex]7th=a+(7-1)d[/tex]
Therefore the First Term is given as
[tex]a=7th-(7-1)d[/tex]
[tex]a=21-6*5\\a=-9[/tex]
Generally the equation for 9th term is mathematically given by
[tex]9th=a+8d[/tex]
[tex]9th=-9+8(5)[/tex]
[tex]9th=31[/tex]
