Question 739221
arithmetic sequence...

d=2, a1=3, an=27, n=?


{{{a[n]=a[1]+(n-1)*d}}}

becomes...

{{{27=3+(n-1)*2}}}


{{{2(n-1)=24}}

{{{n-1=12}}}


so n=13 i.e.

27 is the 13-th term