diff --git a/config/en/mkdocs.yaml b/config/en/mkdocs.yaml
index d6ed6c9..6ef77f0 100755
--- a/config/en/mkdocs.yaml
+++ b/config/en/mkdocs.yaml
@@ -37,6 +37,9 @@ markdown_extensions:
   - pymdownx.mark
   - pymdownx.tilde
   - def_list
+  - admonition
+  - pymdownx.details
+  - pymdownx.superfences
 
 
 extra_javascript:
diff --git a/docs/en/mathematics/set-theory/sets.md b/docs/en/mathematics/set-theory/sets.md
index f05f68f..2ff6ad8 100644
--- a/docs/en/mathematics/set-theory/sets.md
+++ b/docs/en/mathematics/set-theory/sets.md
@@ -28,4 +28,8 @@ Suppose for example that $B = {x,y,z}$, then $\wp(B) = \{\varnothing,\{x\},\{y\}
 Let $B$ be set with $n$ elements. A subset $A$ of $B$ is completely determined by its elements. For each element $b \in B$ there are two options, it is in $A$ or it is not. So, there are $2^n$ options and thus $2^n$ different subsets $A$ of $B$.
 
 </details>
-<br>
\ No newline at end of file
+<br>
+
+??? note "*Proof*:"
+
+    Let $B$ be set with $n$ elements. A subset $A$ of $B$ is completely determined by its elements. For each element $b \in B$ there are two options, it is in $A$ or it is not. So, there are $2^n$ options and thus $2^n$ different subsets $A$ of $B$.
\ No newline at end of file