#!/bin/bash

read -p "How old are you?" age

if [ $age -gt 60 ]
then
  echo "OK Boomer!"
elif [ $age -gt 40 ]
then
  echo "Millenial"
else
  echo "Young Blood."
fi

#here is another way with different brackets
if (( $age > 60 ))
then
  echo "OK Boomer!"
elif (( $age > 40 ))
then
  echo "Millenial"
else
  echo "Young Blood."
fi