Here is a short video that shows how an 11 year old can begin to MASTER the concepts related to constant rate problems and make ordered pairs into simple linear equations without being given formulas to memorize...in fact given time they will be able to come up with the formulas themselves.
We never once talked about dy/dx. He quickly began to see that the fastest way to do it was to take the largest number that would divide equally into each of them and is just beginning to find out that the result is dy/dx but he is doing it by multiplying and subtracting...which by the way is division. Do you see how math really is a language? If you are a layman that paragraph might be jibberish, but if you are a teacher I encourage you to pause and reflect. If you are a homeschooler with math issues of your own take a while and play with the concepts and you will see that it becomes easier the more you play with it.
This student did 15 or 20 minutes for a few sessions over a few days, later one 30 minute session of which this video is part and we haven't been back since but we will and each time we do more understanding is created.
More at my house of math.