Let's simplify the expression \((2 - 3 \cdot 0.9^3) / (2^9 \cdot 0.9^{-10})\) and find an equivalent expression with only positive exponents.
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Rewrite the expression with \( 0.9 \) as \( 9^{-1} \):
\[ (2 - 3 \cdot (9^{-1})^3) / (2^9 \cdot (9^{-1})^{-10}) \]
This simplifies to:
\[ (2 - 3 \cdot 9^{-3}) / (2^9 \cdot 9^{10}) \]
The term \( 3 \cdot 9^{-3} \) can be calculated or left as-is for now.
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Now, combine the fractions:
\[ = \frac{2 - 3 \cdot 9^{-3}}{2^9 \cdot 9^{10}} \]
To combine this, we need to express \( 2 \) with the common denominator of \( 9^{-3} \):
\[ = \frac{2 \cdot 9^3 - 3}{2^9 \cdot 9^{10}} \]
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Now simplifying the numerator, we have \( 2 \cdot 9^3 - 3 \), and when we express it back as a fraction, we will multiply it out by \( 9^{10} \).
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As there is nothing in the expression that will cancel further on this numerator term with the existing expressions given above, we now need to check the simplified versions provided:
Now let's analyze the answer choices:
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Choice A: \( 2^{12} \cdot 9^{-12} / 2^9 \cdot 9^{-10} \)
This can be simplified as: \[ = \frac{2^{12}}{2^9} \cdot \frac{9^{-12}}{9^{-10}} = 2^{12-9} \cdot 9^{-12 + 10} = 2^3 \cdot 9^{-2} \]
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Choice B: \( 2^3 \cdot 9^2 \) does not align with our structure.
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Choice C: \( 2^{-7} \cdot 9^{-1} / 2^9 \cdot 9^{-10} \) gives an incorrect dynamic.
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Choice D: \( 2^3 / 9^2 \) also doesn't take the denominator structure into consideration.
Comparing the final output from A:
From option A: \( 2^3 \cdot 9^{-2} = 2^3 / 9^2\)
So the equivalent expression which can be expressed solely with positive exponents through required simplifications will conclude as choice:
\[ \boxed{2^3 / 9^2} \]