Earning post-graduate math hours after your master's This is in the US, in case it's unclear.

I'm interested in teaching math at the 2-year college level. I have an interdisciplinary MS with a strong engineering focus. I see openings that require "a master's degree in a related field with at least 18 hours in Mathematics".

I looked around for advice and everyone's talking in terms of earning a complete degree.

Is it possible for me to earn these hours in a way that would satisfy (at least some) hiring committees, without having to get a whole extra master's degree?
Many graduate programs have an option for "special graduate students" to enroll on a part time basis.  You could check with universities in your area to see whether or not this is possible. Realize that you'll have to pay tuition and won't be eligible for financial support if you go this route.