The answer is letteer C. You just have to multiply 9 and pi
An arithmetic sequence (a_n) is as follows:

where

is the first term and d is the constant difference,
thus, we see that the n'th term of an arithmetic sequence is

in our particular case d=5, the third term is 8, so we have:

and the general term is

,
Answer: first term is -2, n'th term is -2+5(n-1)
She could've cut the cake into 6 pieces so everyone could have an equal slice of cake or she could've cut it into 12 pieces and everyone could have 2 pieces each equally
hope this helps :)