What was the change in the Basic weighted average number of shares outstanding from 2017 to 2018?
{"": {"January 3, 2020": "", "December 28, 2018": "(in millions)", "December 29, 2017": ""}, "Basic weighted average number of shares outstanding": {"January 3, 2020": 143, "December 28, 2018": 151, "December 29, 2017": 152}, "Dilutive common share equivalentsstock options and other stock awards": {"January 3, 2020": 2, "December 28, 2018": 2, "December 29, 2017": 2}, "Diluted weighted average number of shares outstanding": {"January 3, 2020": 145, "December 28, 2018": 153, "December 29, 2017": 154}}
basic_weighted_average_2018 = df["Basic weighted average number of shares outstanding"]["December 28, 2018"]
basic_weighted_average_2017 = df["Basic weighted average number of shares outstanding"]["December 29, 2017"]
answer = basic_weighted_average_2018 - basic_weighted_average_2017