math
posted by Serena .
a pari of shoes is on sale for 10% off the original price. If the sale price is $14.40, what was the original price of the item?

0.9x = 14.4
x = ? 
x = 16

.9 derives from the fact that you're paying 90/100 or 90% of the original price.
it's basically cross multiply. you want to find the original price (100). thus, the x in the denominator is across the 100
90/100=14.40/x
90x=1440
numerator of the left side multiply to the denominator of the right
=numerator of the right side multiply to the denominator of the left