Fix a missing article

Author: mlouhivu

docs/mooc/python-and-performance/prerequisities.md

@@ -7,7 +7,7 @@ benefit from the course and explain how the course is structured.
 
 -->
 
-In order to succeed in this course, you need to know few things beforehand.
+In order to succeed in this course, you need to know a few things beforehand.
 
 First, this course is aimed at people who already know how to program in
 Python. **We will not be teaching Python programming as such.** However,
@@ -25,7 +25,7 @@ You can test if you have the prerequisite level of skills and knowledge by
 going through the quiz in the next step.
 
 Second, previous knowledge of high-performance computing is not needed, we
-will discuss the relevant topics as we proceed. 
+will discuss the relevant topics as we proceed.
 
 Third, the course duration is four weeks. Each week we discuss a different
 topic related to Python performance. The main aspects of each topic is covered
@@ -36,5 +36,5 @@ best way to learn programming.
 
 We provide simple instructions for setting up a virtual machine with the
 programming environment for the course in your own laptop/workstation. The
-virtual machine is based on Linux, and in order to carry out the exercises 
+virtual machine is based on Linux, and in order to carry out the exercises
 some familiarity with the Linux command line is useful.