Equivalence relation: ① 600 m plain cloth; The number of coats is equal to the number of trousers.
Solution: We assume that X-meter cloth is used to produce tops and Y-meter cloth is used to produce pants.
According to the meaning of the question, X+Y = 600, 2/3x = y.
Solution, x=360y=240.
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It takes 360 meters to produce tops, 240 meters to produce pants, and 240 sets can be produced.