$\"\"$

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The sum of a geometric series is $\"\"$ .

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Where $\"\"$ is first term and r is common ratio.

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The given values are $\"\"$ .

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Subtract denominator: $\"\"$ ) $\"\"$

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Apply multiplication property of equality: a = b then $\"\"$ .

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$\"\"$ (Multiply each side by 0.8)

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$\"\"$ (Cancel common terms)

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$\"\"$ (Evaluate power: $\"\"$ )

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$\"\"$ (Subtract: $\"\"$ )

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$\"\"$ (Multiply: $\"\"$ ) $\"\"$

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Apply division property of equality: a = b then $\"\"$ .

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$\"\"$ (Divide each side by 0.99968)

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$\"\"$ (Cancel common terms)

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$\"\"$ (Divide: $\"\"$ )

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The 4th terms of geometric series $\"\"$ . $\"\"$

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The value of $\"\"$ .