Respuesta :

Hi

arithmetic serie mean that to change from a rank to an other, you add "r"

So :  if 6 is  S1, and  2 is  pace,    

then you need 8 hops to go from S1 to S9.

so you 'r going to add the reason 8 times.

so :  S9 = 6 + 8 * 2   =   6 + 16 = 22

conclusion :  S9 = 22