diff --git a/Advanced/Mock a Mockingbird/main.tex b/Advanced/Mock a Mockingbird/main.tex
index ceba1af..5c0c358 100755
--- a/Advanced/Mock a Mockingbird/main.tex	
+++ b/Advanced/Mock a Mockingbird/main.tex	
@@ -10,7 +10,7 @@
 \usepackage{alltt}
 
 
-\newenvironment*{helpbox}[1][0.5]{
+\newenvironment{helpbox}[1][0.5]{
 	\begin{center}
 	\begin{tcolorbox}[
 		colback=white!90!black,
diff --git a/Advanced/Mock a Mockingbird/parts/01 tmam.tex b/Advanced/Mock a Mockingbird/parts/01 tmam.tex
index 12429a3..e8a37e2 100644
--- a/Advanced/Mock a Mockingbird/parts/01 tmam.tex	
+++ b/Advanced/Mock a Mockingbird/parts/01 tmam.tex	
@@ -164,7 +164,7 @@ Show that any bird that is fond of at least one bird is compatible with itself.
 \begin{solution}
 	\begin{alltt}
 		let A
-		let x so that Ax := x
+		let x so that Ax = x
 		Ax = x  \qed{}
 	\end{alltt}
 	That's it.