I have a BA (from Coe College in Cedar Rapids IA) with extensive coursework in Math & Physics. I have tutored math and computer subjects (off and on) since 1972. I have been an adjunct instructor for a local career college, teaching programming, and Microsoft Access Database. I have 19 years career experience in computer programming.
More importantly, I think, is that I take the necessary time and trouble to express myself clearly, adjusting the level and pace of my lessons to the needs of the student.
As an example, it doesn't matter if I can derive the generic solution to quadratic equations or not. What will matter is that if you or your child needs to be able to apply the quadratic equations formula, that you, or he or she can learn to do it, and pass the test.
You only fail if you stop trying.