[Math] Show that the argument form with premises (p∧t)→…¬s and conclusion q→r is valid

discrete mathematicslogic

Stuck on this problem. I want to use the rules of inference to show that the argument form with premises (p∧t)→(r∨s), q→(u∧t),u→p, and ¬s and conclusion q→r is valid. Would really appreciate if someone can help me solve it and explain which rules they used

Best Answer

$\neg s$ premise $1$

$(p \wedge t) \to (r \lor s)$ premise $2$

$(p \land t) \to r$ based on $1$ and $2$ Disjunctive Syllogism

$q \to (u \land t)$ premise $4$

$q \to r$ (hypothetical syllogism) from $3$ and $4$

Is this answer correct? I am not sure if $(p \land t) == (u \land t)$. Because based on Hypothetical syllogism, $P \to Q$ and $Q \to R \implies P \to R$. In this cause I am taking $(p \land t) == (u \land t) == Q$