Questionnaire-2024/natural_deduction_propositional_logic/0020_sol.tex

\begin{logicproof}{2}
(p \implies q)
    \implies r & \prem \\
    \begin{subproof}
        \lnot r \land \lnot s & \assum \\
        \lnot r & $\ande{1} 2$ \\
        \lnot (p \implies q) & $\MT 1,3$
    \end{subproof}
    \lnot r \land \lnot s \implies \lnot (p \implies q) & $\impi 2-4$
\end{logicproof}