I'd like to know what you've tried
But here's some hints, sort has some options to randomize lists of information, head or tail can be set to limit output (perhaps to 150) and while loops can read lines of text from output of commands.
while read i; do echo "$i"; done <<< $(command)
See man pages for sort and head or tail.
I don't know if find can delete a random list of exactly 150 though.
However, combining the above makes it pretty easy.