It is given that
- $SA = B \land \neg C$
- $SB =A \to C$
- $SC = \neg C \land (A \lor B)$
How do I get $(SA \land SB \land SC) \to (B \land \neg A \land \neg C)$?
I did this (below) but now I'm stuck.
$$B \land \neg C \land A \to C \land \neg C \land (A \lor B) \\ = \neg C \land (B \land (A \lor B)) \land \neg A \lor C$$
So you have:
$\begin{align}&(B\wedge\neg C)\wedge(A\to C)\wedge(\neg C\wedge (A\vee B)) \\&(B\wedge\neg C)\wedge(\neg A\vee C)\wedge(\neg C\wedge(A\vee B))&&\text{by conditional equivalence}\\&\neg C\wedge\neg C\wedge B\wedge (A\vee B)\wedge (\neg A\vee C)&&\text{by association and commutivity}\\&\neg C\wedge B\wedge (A\vee B)\wedge (\neg A\vee C)&&\text{by idempotence}\end{align}$
That checks out okay. So, now use absorption: $B\wedge (A\vee B)~=~B$ $$\begin{align}&B\wedge (A\vee B)\\&(B\vee \bot)\wedge(B\vee A)\\&B\vee(\bot\wedge A)\\&B\vee\bot\\&B\end{align}$$
Next use distribution, and the path should be clear from then on.