Update variables5.rs

Author: 13001288072

exercises/variables/variables5.rs

@@ -1,12 +1,11 @@
-// variables5.rs
-//
-// Execute `rustlings hint variables5` or use the `hint` watch subcommand for a
-// hint.
-
-
 fn main() {
+    // 1. 声明变量number，绑定字符串值"T-H-R-E-E"（类型：&str）
     let number = "T-H-R-E-E"; // don't change this line
+    // 2. 打印字符串：输出 "Spell a Number : T-H-R-E-E"
     println!("Spell a Number : {}", number);
+    
+    // 3. 变量遮蔽：用let重新声明同名变量number，绑定整数值3（类型：i32）
     let number = 3; // don't rename this variable
+    // 4. 打印计算结果：3 + 2 = 5，输出 "Number plus two is : 5"
     println!("Number plus two is : {}", number + 2);
 }