Step-by-Step:
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1. We are given the following:
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This being said, the first thing we need to do is switch sides, writing it as follows:
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2. Next, we need to add 9.9 to both sides of the equation.
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3. Then, we simplify.

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4. Now, we add 1 to both sides of the equation.
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5. We simplify again.

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6. Next, we divide both sides by 10.
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7. Finally, simplify one more time.
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Hence, out solution is
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Hope this helps!