When I first read the examples I wasn't exactly sure what they referred to. I was looking for the examples to be about reuse, remix and share (from the sentence just prior), but the first is more about building on previous knowledge and imho this concept doesn't need an example. I think we should identify the purpose of the examples as a way to inform how we might improve them.
Also, I don't see order of operations as a pre-requisite to basic arithmetic. Basic arithmetic operations are learned in isolation in the elementary grade. It's probably better to say that order of operations is pre-requisite knowledge to solving algebraic equations which include more than one type of arithmetic operation.
I think you're right -- the linkage between the preface sentences and examples can be improved :-).
The "logic" is that sharing knowledge is a foundational value of education and in many respects reuse is dependant on a willingness to share. So we need to tighten up the examples --- I'll take a look and reword a little. Let me know if the result is better and improve where you can.
Total agreement on the revision re order of operations. You can see I don't teach Math ;-)
The revised lead up is much improved. I like that it clearly states that building on existing knowledge is an instance of reuse. I didn't make that connection at first.
I messed a bit more with the math example. It's hard to make the second sentence correct and user-friendly. Maybe we should delete it: people who know algebra will know why its a pre-requisite without our saying why and for people who don't the further explanation seems confusing. Just a thought.
I think the lead-up works better now as well.
I'm OK with dropping the second sentence with the order of operations -- it was included for those who may not be familiar with the concept. Given that its an example -- it should be OK to delete this.
I made another attempt at the example to simplify the explanation. I think this one works OK. I agree it's nice to have a little bit of explanation/example for those unfamiliar with the concept.