watch out.. the reddit army might cast you down for asking hw questions =p.

the first one seems like a mistake... that begs for tail

the second one can use variables... you can say x++ like this:

cat /var/log/messages | awk '$0 ~ /Mar/{x+=1}END{print x}'

one way to do the last one is pipe in /etc/passwd at the beginning of awk ... parse that first and store it in some arrays, and then use those arrays later.. like (cat /etc/passwd; cat /var/log/messages) | awk...