Question 970884
  Notice this is an arithmetic series. Must use the formula to find the explicit formula.  

{{{d = 10}}} is common difference between each two consecutive terms, 

first term is {{{6}}} and counting the terms, the fourth term is {{{36 }}}; so, the number of the terms is {{{n}}}={{{1}}},{{{2}}},{{{3}}},{{{4}}}

then nth term formula is:

{{{6+ (n - 1)10}}}  where {{{n}}}={{{1}}},{{{2}}},{{{3}}},{{{4}}}

check:
if {{{n=1}}}
{{{6+ (1 - 1)10 =6+0=6}}}
if {{{n=2}}}
{{{6+ (2 - 1)10 =6+10=16}}}
if {{{n=3}}}
{{{6+ (3 - 1)10 =6+20=26}}}
if {{{n=4}}}
{{{6+ (4 - 1)10 =6+30=36}}}

then
{{{sum(6+ (n - 1)10=6+16+26+36=84,1,4)}}}