I think not, based on feedback from DS1. If it is it would probably be at the lower level, x+7=10, 2x+1=11, so I would familiarise with the concept of the unknown quantity rather than teaching theory.
As it is multiple choice you can always feed the answers back into the question, if you have enough time.
We did far to much preparation on Maths for Reading, the hardest questions did seem like those at the end of a KS2 paper rather than some of the tough 11+ maths papers.
However as Reading do not provide guidance they could sneak it in.