Help 2 ​

2. 

c_n  = 3n  - 1          replace n with  15    and we have

c₁₅  =  3(15)  - 1   =   45  - 1   =  44

3.  The recursive formula  is

a_n  = a_n-1 + 6,    a₁  = 7    { This  "formula" means that are taking the previouis term and adding 6 to it to get the next term  }

To get the next term we have

31  +  6   = 37    {The first answer }