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I think of a number.
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I add 13 to it and then divide by three.
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The answer is 12.
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What number did I think of?
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By letting the number I was thinking of be 𝑥, we can set up an equation.
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In this example, we firstly added 13 to the number, 𝑥 plus 13.
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We then divided by three.
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This gives us 𝑥 plus 13 divided by three.
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The answer was 12.
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Therefore, 𝑥 plus 13 divided by three is equal to 12.
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In order to solve this equation, we firstly need to multiply both sides by three.
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This gives us 𝑥 plus 13 is equal to 36, as 12 multiplied by three is 36.
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Subtracting 13 from both sides of this equation gives us a value of 𝑥 equal to 23.
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This means that the number I was thinking of initially was 23, as 23 plus 13 divided by three is equal to 12.