When a sale is 10% off, this means they subtracted 10% of the original price from the original price, and the buyers now only have to pay 90% of the price (100-10=90).
This means $14.40 is 90% of the original, so we can use ratios to figure out 100% of the price.
14.40 90%
x 100%
x = 14.40 * 100 / 90 = 16
So, 16 dollars was the original price.