updated dictionary

Updated question and answer in section **Dictionaries Challenges** based on corresponding section in episode [01-short-introduction-to-Python.md](https://github.com/datacarpentry/python-ecology-lesson/blob/gh-pages/_episodes/01-short-introduction-to-Python.md)

Author: NPalopoli

_extras/guide.md

@@ -40,12 +40,19 @@ installation. Otherwise, it will tell you that the system is good to go and read
 	`tuple`
 
 ### Dictionaries Challenges
-* Can you do reassignment in a dictionary? Give it a try.
+
+* Changing dictionaries: 2. Reassign the second value.
 
 Make sure it is also clear that access to 'the second value' is actually just about the key name. Add for example `rev[10] = "ten"` to clarify it is not about the position.
 
-* You should see the following output:
-`{1: 'one', 2: 'two', 3: 'three'}`
+~~~
+rev
+~~~
+{: .language-python}
+~~~
+{1: 'one', 2: 'two', 3: 'three'}
+~~~
+{: .output}
 
 ~~~
 rev[2] = "apple-sauce"
@@ -55,7 +62,7 @@ rev[2] = "apple-sauce"
 ~~~
 {1: 'one', 2: 'apple-sauce', 3: 'three'}
 ~~~
-{: .language-python}
+{: .output}
 
 ## 02-starting-with-data