In pure answer to the question, any of the solutions provided by Why do the less than symbol (
<) and the greater than symbol (
>) appear wrong as upside down exclamation or question mark? will solve the problem. The easiest is probably to add
to your document preamble. However...
...when using mathematical expressions, maintain the appropriate spacing by keeping the context mathematical. I would therefore suggest the following:
The operator spacing between the relations
= will be kept better than using your original
$valuea$ < $valueb$.
You may also consider transitioning to the more flexible