fix typo for part4a (en)

Author: mayconblopes

src/content/4/en/part4a.md

@@ -495,7 +495,7 @@ module.exports = {
 }
 ```
 
-> The _average_ function uses the array [reduce](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce) method. If the method is not familiar to you yet, then now is a good time to watch the first three videos from the [Functional Javascript](https://www.youtube.com/watch?v=BMUiFMZr7vk&list=PL0zVEGEvSaeEd9hlmCXrk5yUyqUag-n84) series on Youtube.
+> The _average_ function uses the array [reduce](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce) method. If the method is not familiar to you yet, then now is a good time to watch the first three videos from the [Functional Javascript](https://www.youtube.com/watch?v=BMUiFMZr7vk&list=PL0zVEGEvSaeEd9hlmCXrk5yUyqUag-n84) series on YouTube.
 
 There are many different testing libraries or <i>test runners</i> available for JavaScript. In this course we will be using a testing library developed and used internally by Facebook called [jest](https://jestjs.io/), which resembles the previous king of JavaScript testing libraries [Mocha](https://mochajs.org/).
 
@@ -665,7 +665,7 @@ describe('average', () => {
 
 Describe blocks can be used for grouping tests into logical collections. The test output of Jest also uses the name of the describe block:
 
-![screenshot of npm test shwoing describe blocks](../../images/4/4x.png)
+![screenshot of npm test showing describe blocks](../../images/4/4x.png)
 
 As we will see later on <i>describe</i> blocks are necessary when we want to run some shared setup or teardown operations for a group of tests.