The original prices of the guitars are 100%. Example: for the $160 guitar, $160 would be 100% of the price. The new price is $100. The guitar went down $160-$100=$60. 60/160 = 0.375. Convert that into a percentage. 0.375 = 37.5%. Guitar number one has decreased by 37.5%. Guitar number 2: $250 = 100%. It went down $250-$150=$100. 100/250 = 0.40. Convert to percentage. 0.40 = 40%. Guitar 1 had a decrease of 37.5% in price Guitar 2 had a decrease of 40% in price. Hope this helps!