diff --git a/en/src/basic-types/numbers.md b/en/src/basic-types/numbers.md
index dc525d2..72d0a28 100644
--- a/en/src/basic-types/numbers.md
+++ b/en/src/basic-types/numbers.md
@@ -93,14 +93,19 @@ fn main() {
 
 ```rust,editable
 
-//  Replace ? with your answer
+// Fill the blank to make it work
 fn main() {
     let x = 1_000.000_1; // ?
     let y: f32 = 0.12; // f32
     let z = 0.01_f64; // f64
 
+    assert_eq!(type_of(&x), "__".to_string());
     println!("Success!");
 }
+
+fn type_of<T>(_: &T) -> String {
+    format!("{}", std::any::type_name::<T>())
+}
 ```
 
 8. 🌟🌟 Make it work in two distinct ways