find out a number after a percentage is deducted

the number is $350

reduce it by 10%

well 100% of the price  $350

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so 10% is $35

reduce means make smaller

$350-$35=$315  is the reduced price

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or you can say that the original price IS 100%

reduce it by 10%      100-10=90%

90%of  $350 = 90/100*350 = $315

You can do it either way