you want sum of resolved of each agent id and get the highest one ? If so then you can do something like this
$higest_resolved=DB::select(DB::raw('SELECT agentid,SUM(resolved)
as resolved_total FROM table_name GROUP by agentid ORDER by resolved_total DESC LIMIT 1'));
for adding month and year condition,you can do as
$higest_resolved=DB::select(DB::raw('SELECT agentid,SUM(resolved)
as resolved_total,reportyear,reportmonth FROM table_name where reportmonth="'.$currentMonth.'" and reportyear="'.$currentYear.'" GROUP by agentid,reportyear,reportmonth ORDER by resolved_total DESC'));
you can still add limit 1 at end to get only one value.