Question 756896
You would be looking for an arithmetic series equal to 30, built on a sequence of consecutive natural numbers and 7 terms.  


{{{30=7(a[1]+a[n])/2}}}  and we do not know yet {{{a[1]}}} or {{{a[n]}}}.  You also expect {{{a[n]-a[1]=6}}}.


With that, you now have two equations and two unknowns, as a set of linear equations.