You bought a phone for $640.00. It has been on sale for 20% off. What was the phone's original price?
+128407 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
+1904 Let x = phone's original price
Let 0.2 (20%) = discount of phone
Let 640 = price of phone after discount
\(0.2x=x-640\)
\(0.2x-x=x-640-x\)
\(-0.8x=x-640-x\)
\(-0.8x=-640-0\)
\(-0.8x=-640\)
\(\frac{-0.8x}{-0.8}=\frac{-640}{-0.8}\)
\(1x=\frac{-640}{-0.8}\)
\(x=\frac{-640}{-0.8}\)
\(x=800\)
