Does anyone know the answer

Simplify (a/b - b/a) times (a - a^2/a+b) a - a^2/a=b is a mixed number

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Twenty points. suppose that one doll house uses the 1 inch scale, meaning that 1 inch on the doll house corresponds to 1/2 foot for life-sized objects. if the doll house is 108 inches wide, what is the width of the full-sized house that it's modeled after? in inches and feet