fixed typo

21_Day_DOM/21_day_dom.md

@@ -351,7 +351,7 @@ As you have notice, the properties of css when we use it in JavaScript is going
 ### Exercise: Level 1
 
 1. Create an index.html file and put four p elements as above: Get the first paragraph by using **_document.querySelector(tagname)_** and tag name
-2. Get get each of the the paragraph using **_document.querySelector('#id')_** and by their id
+2. Get each of the the paragraph using **_document.querySelector('#id')_** and by their id
 3. Get all the p as nodeList using **_document.querySelectorAll(tagname)_** and by their tag name
 4. Loop through the nodeList and get the text content of each paragraph
 5. Set a text content to paragraph the fourth paragraph,**_Fourth Paragraph_**