$Q\to R = T\to F = F$, so $P\to(Q\to R)=T\to F=F$.
$P\to Q = T\to T = T$, $P\to R = T\to F = F$, hence $(P\to Q)\to(P\to R)=T\to F=F$.
Therefore $(F)\to(F)=T$.
Also $Q\vee R = T\vee F = T$, so $P\to(Q\vee R)=T\to T=T$.
1
The contrapositive of $p \to (\neg q \to \neg r)$ is —
Consider the following statements:
S1: There exists infinite sets A, B, C such that A ∪ C = B ∪ C is finite.
S2: There exist two irrational numbers x and y such that (x+y) is rational.
Which of the following is true about S1 and S2?