add chapter [Advanced use and pub]

solutions/crate-module/use-pub.md

@@ -0,0 +1,39 @@
+1.
+```rust
+use std::fmt::Result;
+use std::io::Result as IoResult;
+
+fn main() {}
+```
+
+2.
+```rust
+use std::collections::*;
+
+fn main() {
+    let _c1:HashMap<&str, i32> = HashMap::new();
+    let mut c2 = BTreeMap::new();
+    c2.insert(1, "a");
+    let _c3: HashSet<i32> = HashSet::new();
+}
+```
+
+```rust
+use std::collections::{HashMap, BTreeMap, HashSet};
+
+fn main() {
+    let _c1:HashMap<&str, i32> = HashMap::new();
+    let mut c2 = BTreeMap::new();
+    c2.insert(1, "a");
+    let _c3: HashSet<i32> = HashSet::new();
+}
+```
+
+
+3. 
+```rust
+// in lib.rs
+
+// Add this line
+pub use crate::front_of_house::hosting;
+```