if it is an arithmetic progression
[tex]\displaystyle\bf \boxed{S_n=\frac{a_1+a_n}{2} \cdot n\quad; \quad a_n=a_1+(n-1)r}\\\\\\S_9=\frac{6+6+16}{2} \cdot9=126\\\\\\Answer: \boxed{S_9=126}[/tex] if it is a geometric progression [tex]\displaystyle\bf \boxed{ S_n=\frac{a_1(1-r^n)}{1-r} \quad }\\\\\\S_9=\frac{6(1-2^9)}{1-2} =511\cdot6=3066\\\\\\Answer:\boxed{ S_9=3066}[/tex]
