Bash: grep pattern from command output

Question

I\'m really new with bash, but it\'s one of the subjects on school. One of the exercises was:

Give the line number of the file \"/etc/passwd\" where the informat

Answer 1

cat /etc/passwd -n | grep `whoami` | cut -f1 

Surrounding a command in ` marks makes it execute the command and send the output into the command it's wrapped in.