subtraction is giving me a syntax error

[Joel Pendery]

So I am trying to write a bit of code and a simple numerical
subtraction

y_diff = y_diff-H

is giving me the error

Syntaxerror: Non-ASCII character '\x96' in file on line 70, but no
encoding declared.

Even though I have deleted some lines before it and this line is no
longer line 70, I am still getting the error every time.  I have tried
to change the encoding of the file to utf-8 but to no avail, I still
am having this issue.  Any ideas?

Thanks in advance