Problem with distortion of equations as a result of modifying other styles

[Zahra]

There is a book written in word, its normal style formatting was Calibri. I was working on a part of this book and i changed its formatting to Cambria Math mistakenly. When I noticed the problem I modified the style to Calibri again, but all of the letters in equations distorted and changed to an unknown sign. How can I solve this problem?
Thanks for any help


regards