Ursula is working at a marketing firm. She created a 30-second long commercial. Her boss told her that this commercial is too long to air and told her to shorten the commercial by 30%. How long will this commercial be after Ursula makes the desired changes? Let's think first. Chain of thought:
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Ursula's boss want's the commercial to be 30 / 100 * 30 = 9 seconds shorter. After Ursula makes the desired changes, the ad is going to be 30 - 9 = 21 seconds long.
Therefore, the answer is 21.
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