Well, it said "for a year."

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I think teaching the language of algebra at an early age is a good thing, because many kids who fail algebra do so because they can't make the conceptual shift of using letters to stand in for unknown or varying values. But let's not confuse language with understanding and applying the rules and concepts to solve problems.

What DD is doing is more complex than 9 + x = 10, which is introduced in grade 1 these days. (Although at that point, they don't teach them to solve it in the "algebraic" way.) FI, the answer to that question was not x + 4.