Hey!
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This is also known as finding the "percent of change".
Formula: [tex]\frac{New~Value~-~Old~Value}{Old~Value}*100~percent[/tex]
~Solve
[tex]\frac{76~-~80}{80} = \frac{-4}{80} = -0.05 * 100~percent = -5~percent[/tex]
Change it back to positive.
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Hence, the dress was decreased by 5%
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Hope This Helped! Good Luck!