$\"\"$ $\"\"$

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The word “decreased” indicates the symbol “ $\"\"$ ”.

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The word “equals” indicates the symbol “ $\"\"$ ”

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Let $\"\"$ resents the number.

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Rewrite the sentence into equation,

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$\"\"$ $\"\"$

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The equation is $\"\"$

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According to addition property of equality: Add 77 to each side.

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$\"\"$

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$\"\"$ (Apply additive inverse property: $\"\"$ )

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$\"\"$ (Apply additive identity property: $\"\"$ )

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$\"\"$ (Add: $\"\"$ ) $\"\"$

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Check:

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To check the solution, substitute $\"\"$ in original equation.

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$\"\"$

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

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Compare the values, the equation is true. The solution is $\"\"$ . $\"\"$

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The number is $\"\"$ .