The price dropped 299.99 - 180.55 = 119.44. So we need to find out what percentage 119.44 is of 299.99.
"119.44 is what percentage of 299.99" translates to
119.44 = x * 299.99
So x = 119.44 / 299.99 = about 0.3981466, which is 39.81% when rounded to the nearest hundredth of a percent.
