Fix typo in Section 12.1 of the Open Logic Text

Author: FnControlOption

content/first-order-logic/axiomatic-deduction/rules-and-proofs.tex

@@ -73,8 +73,8 @@
 \item for some $j < i$, $!A_j$ is $!B \lif !A_i$, and for some $k < i$,
   $!A_k$ is~$!B$.
 \end{enumerate}
-The last clause says that $!A_i$ follows from~$!A_j$ ($!B$) and $!A_k$
-($!B \lif !A_i$) by modus ponens. If we can go from $1$ to~$n$, and
+The last clause says that $!A_i$ follows from~$!A_j$ ($!B \lif !A_i$) and $!A_k$
+($!B$) by modus ponens. If we can go from $1$ to~$n$, and
 each time we find !!a{formula}~$!A_i$ that is either in~$\Gamma$, an
 axiom, or which a rule of inference tells us that it is a correct
 inference step, then the entire sequence counts as a correct