title: r markdown equation cannot knit correctly in Word 2016
body: <p>I had a strange situation. The temperature equation cannot be knitted correctly in a Word document (Word 2016), while the other equation works just fine. I am showing the screenshots and hoping to have suggestions about what is wrong here. I appreciate any help. :-D</p>
  <p>The equations in the Word output:
  <a href="https://i.stack.imgur.com/seLHI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/seLHI.png" alt="enter image description here" /></a></p>
  <p>The equation shows in RStudio:</p>
  <p><a href="https://i.stack.imgur.com/Zw8Fd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Zw8Fd.png" alt="enter image description here" /></a></p>
  <p>The equation shows in HTML output:
  <a href="https://i.stack.imgur.com/2YkST.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2YkST.png" alt="enter image description here" /></a></p>
  <p>Here I used a generic script to test the equation codes.</p>
  <pre><code>---
  title: &quot;test_equation&quot;
  date: &quot;9/16/2020&quot;
  output: word_document
  ---
  
  ```{r setup, include=FALSE}
  knitr::opts_chunk$set(echo = TRUE)
  ```
  
  The equation doesn't show in the Word:  
  
  $$\Delta Temperature = \frac{\Delta Heat}{Density\times{Specific}\space{Heat}\times{\Delta Flow}\space{Volume}}$$
  
  -------------------------------------------
  The equation shows in the Word:
  $$ME = \frac{1}{n}\sum(X_{sim} - X_{obs})$$
  </code></pre>