1. Do they seem to have been taught a different method for something you remember? Not a problem: get them to #teach you theirs, and encourage them to try to understand yours. See if you can spot similarities. Why do both work? Can you find reasons why one may be "better" than the other (there are no right answers here, but just being more familiar doesn't count)?
2. Are they doing something you don't recognise, or maybe you do recognise but never got the hang of it? Get them to #teach you as much of it as they can. Work together on it. Admit that you don't understand it YET but don't use this as an excuse to not engage. Learning new things is a positive thing. Not understanding something is a prerequisite for learning something new.
@TeaKayB I have the opposite problem: I like math, and when I express what I think are positive or reassuring thoughts about material she finds difficult, the message my daughter gets is "this is easy for me; why isn't it easy for you?" and she feels insulted or dismissed. I need to find a way of acknowledging her frustration without contributing to it.
@mattmcirvin I think part of the issue (generally) is that finding maths difficult means that maths is bad. The major difference, as far as I can tell, between people who love maths and those who hate it is not whether they find it difficult but how they react to that feeling.
Maybe, rather than trying to reassure her about the _material_, focus on the feelings. You're finding it difficult? That's great! It means you're learning something! Or, it _is_ difficult, I've just had more practise.