To quickly solve a linear equation, a child must be able to INSTINCTIVELY recognize the equivalence of forward & reverse verbs: minus is equivalent to plus negative, and divide is equivalent to times reciprocal. See the Peel section.
Also, the child will need learn distributive property, which we call "spread" for short.
WARNING: the next vocabulary is a bit risque and should be used with discretion. The intent is to add comedic value -- nothing more. The term "solve" is nice and short, but too generic and not at all suggestive. Solve means to make the target variable bare, with nothing else attached to it. Parents with a sense of humor may consider the term "nudify", which can add comic relief, and be more suggestive of the task to be performed.