Answer
$d=s$
$a_{n}=2+\left( n-1\right) \times s$
$ a_{5}=2+4s;$
$a_{100}=2+99s$
Work Step by Step
$t=a_{n+1}-a_{n}=\left( 2+s\right) -s=\left( 2+2s\right) -\left( 2+s\right) =s$
$a_{n}=a+\left( n-1\right) d\Rightarrow a_{1}=a+\left( 1-1\right) d=a=2$
$a_{n}=a+\left( n-1\right) d=2+\left( n-1\right) \times s$
$a_{n}=2+\left( n-1\right) \times s\Rightarrow a_{5}=2+\left( 5-1\right) \times s=2+4s;a_{100}=2+\left( 100-1\right) s=2+99s$