$ awk '{
for(i=1; i<=NF; i+=2)
    names[$i] = ((names[$i]) ? names[$i]+$(i+1) : $(i+1))
}
END{
    for (name in names) print name, names[name]
}' quest
Tom 200
John 10

xargs -n2 < file|awk '{a[$1]+=$2}END{for (i in a) print i,a[i]}'

Tom 200
John 10

awk '{for (i=1;i<=NF;i+=2) a[$i]+=$(i+1)}END{for (i in a) print i,a[i]}' file

Tom 200
John 10

$ echo 'Tom 100 John 10 Tom 100' | grep -o '[0-9]*' | paste -sd+ | bc
210

100
10
100

100+10+100

awk '/Tom/{
     for(i=1;i<=NF;i++)
     if($i=="Tom")s+=$(i+1);
     print "Tom",s;s=0}' your_file

awk -v RS=" " '{n=$1;getline;a[n]+=$1} END {for (i in a) print i,a[i]}' quest
Tom 200
John 10

cat quest
Tom 100 John 10 Tom 100
Paul 20 Tom 40 John 10

awk -v RS=" |n" '{n=$1;getline;a[n]+=$1} END {for (i in a) print i,a[i]}' quest
Paul 20
Tom 240
John 20

awk -v RS=" |n" 'NR%2 {n=$1;next}{a[n]+=$1} END {for (i in a) print i,a[i]}' quest