You bought a phone for $640.00. It has been on sale for 20% off. What was the phone's original price?

Guest Sep 11, 2017

#1**+2 **

Let the original price = P

And 20% off the original price = .20P

So

Original Price - [ 20% off ] = 640 ... so..

P - .20P = 640 simplify

.80P = 640 divide both sides by .80

P = 640 / .80 = 800

So.....the original price was $800

CPhill
Sep 12, 2017

#3**+1 **

Let x = phone's original price

Let 0.2 (20%) = discount of phone

Let 640 = price of phone after discount

\(0.2x=x-640\)

\(0.2x-x=x-640-x\)

\(-0.8x=x-640-x\)

\(-0.8x=-640-0\)

\(-0.8x=-640\)

\(\frac{-0.8x}{-0.8}=\frac{-640}{-0.8}\)

\(1x=\frac{-640}{-0.8}\)

\(x=\frac{-640}{-0.8}\)

\(x=800\)

gibsonj338
Sep 12, 2017