The percent of increase or decrease = change/original x 100%
Since the original price of the watch is $39
Since its price now is $17.50, then
The change of the price = 39 - 17.50 = 21.50 dollars
The percentage of decrease = 21.50/39 x 100%
The percentage of decrease = 55.1282
Round it to the nearest tenth
The percentage of decrease is 55.1%