diff --git a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/40.classical-mechanics/10.main/textbook.fr.md b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/40.classical-mechanics/10.main/textbook.fr.md
index 58c46a6a7..280e0f604 100644
--- a/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/40.classical-mechanics/10.main/textbook.fr.md
+++ b/00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/40.classical-mechanics/10.main/textbook.fr.md
@@ -254,12 +254,12 @@ remember to replace (auto-tra) with your initials (YYY).
 [EN] Galileo's transformations
 
 $`\mathbf{
-\left\{\begin{matrix}
+\left\{\begin{array}{r}
 t'=t \\
 x'=x-V_x\,t \\
 y'=y-V_y\,t \\   
 z'=z-V_z\,t 
-\end{matrix}
+\end{array}
 \right.
 }`$