DOCS-9188: the $gt operator requires the $

Author: schmalliso

source/core/index-compound.txt

@@ -79,7 +79,7 @@ as well as both ``item`` and ``stock`` fields:
 .. code-block:: javascript
 
    db.products.find( { item: "Banana" } )
-   db.products.find( { item: "Banana", stock: { gt: 5 } } )
+   db.products.find( { item: "Banana", stock: { $gt: 5 } } )
 
 For details, see :ref:`compound-index-prefix`.
 

source/tutorial/sort-results-with-indexes.txt

@@ -63,7 +63,7 @@ appear in the index. For example, an index key pattern ``{ a: 1, b: 1
 1 }``.
 
 For a query to use a compound index for a sort, the specified sort direction
-for all keys must match the index
+for all keys in the :method:`cursor.sort()` document must match the index
 key pattern *or* match the inverse of the index key pattern.
 For example, an index key pattern ``{ a: 1, b: -1 }`` can
 support a sort on ``{ a: 1, b: -1 }`` and ``{ a: -1, b: 1 }`` but **not**