use strict;
use warnings;
use List::Util qw(sum);

my %data;
while (<DATA>) {
    next if /^id/;
    my ($id, @cols) = split;
    push @{ $data{$id} }, \@cols;
}

for my $id (sort keys %data) {
    for my $aref (@{ $data{$id} }) {
        print "$id ", sum(@{$aref}), "\n";
    }
}

__DATA__
id   col1   col2    col3
12   100    12        196        
12   120    15        190
13   90     190        200
13   70       20       20 
13   101    340        25 
14   100    123        19 
15   80     389        39 

##</code><code>##

12 308
12 325
13 480
13 110
13 466
14 242
15 508