I'm going to write the phrase sideways, OK. you can use this method if you need to.
six=6
less than= < or -
eight=8
times=x
(a) number=n
then you rewrite what you have beside the words.
6 {< or -} 8n
unless it says 'is less than', you put a subtraction sign. reword afterwords.
8n-6
that is your answer!