Final answer:
Juanita's ability to solve the math problem places her in Piaget's concrete operational stage.
Step-by-step explanation:
In Piaget's theory of cognitive development, Juanita's ability to solve the math problem (35xy^2)(6zy^3) places her in the concrete operational stage.
This stage occurs from about 7 to 11 years old and is characterized by the ability to think logically about real events and perform mathematical operations.
Children in this stage also understand the concept of conservation, where the quantity or properties of an object remain the same even if its appearance changes.
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