What does $x*$ mean?

Question

I am trying to understand what the operator $*$ means in Boolean algebra. If x is a Boolean variable, what does the expression $x*$ mean?

Answer 1

In these exercises, $s*$ means the dual of $s.$ This is obtained from $s$ (which is an expression of propositional calculus containing only the operations $\wedge, \vee,$ and $\neg$) by replacing $\wedge$ with $\vee$, $\vee$ with $\wedge$, $T$ with $F$, and $F$ with $T$.

In the edition of the book I looked at, the author defines dual just before exercise 34, a few exercises above the one the OP referenced in a comment.