Catherine paid $185.30 for an mp3 player. if the price paid includes a 9% sales tax, which of the following equations can be used to determine the price of the mp3 player before tax? (let x represent the cost of the mp3 player and y represent the total cost after tax.)

y = $185.30

x = the orignal cost minus 9% or .09. To increase an objects value by 9% you need to multiply by 1 + .09 or 1.09. So, x being increases by 9% would equal y or $185.30

1.09x = y

1.09x = $185.30

Divide both sides by 1.09

x = $170

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