Find all files with the extension ".txt" in the current directory and its subdirectories up to 3 levels deep, print the results, and replace any numbers in the filenames with a space followed by the number, then sort the results numerically by the number.
`find / -maxdepth 3 -name "*.txt" -print | sed 's/\(\(.*\)\([[:digit:]]\)\)/\1 \3/g' |sort -n -k 2`