Add solution

solutions/basic-types/numbers.md

@@ -64,10 +64,17 @@ fn main() {
 7.
 
  ```rust
- fn main() {
+fn main() {
     let x = 1_000.000_1; // f64
     let y: f32 = 0.12; // f32
     let z = 0.01_f64; // f64
+
+    assert_eq!(type_of(&x), "f64".to_string());
+    println!("Success!");
+}
+
+fn type_of<T>(_: &T) -> String {
+    format!("{}", std::any::type_name::<T>())
 }
  ```
 
@@ -140,4 +147,4 @@ fn main() {
     println!("1 << 5 is {}", 1u32 << 5);
     println!("0x80 >> 2 is 0x{:x}", 0x80u32 >> 2);
 }
-```
+```