What was the percentage change in Selling, general, and administrative expenses in 2019 from 2018?
{"": {"2019": "", "2018": "(in millions)", "2017": ""}, "Net sales": {"2019": 41, "2018": 702, "2017": 928}, "Cost of sales": {"2019": 50, "2018": 602, "2017": 653}, "Gross margin": {"2019": -9, "2018": 100, "2017": 275}, "Selling, general, and administrative expenses": {"2019": 11, "2018": 48, "2017": 50}, "Research, development, and engineering expenses": {"2019": 3, "2018": 39, "2017": 40}, "Restructuring and other charges (credits), net": {"2019": 3, "2018": 30, "2017": -3}, "Operating income (loss)": {"2019": -26, "2018": -17, "2017": 188}, "Non-operating income, net": {"2019": "\u2014", "2018": "\u2014", "2017": 22}, "Pre-tax income (loss) from discontinued operations": {"2019": -26, "2018": -17, "2017": 210}, "Pre-tax gain (loss) on sale of discontinued operations": {"2019": -86, "2018": -2, "2017": 3}, "Income tax (expense) benefit": {"2019": 10, "2018": "\u2014", "2017": -70}, "Income (loss) from discontinued operations, net of income taxes": {"2019": -102, "2018": -19, "2017": 143}}
selling_2019 = df["Selling, general, and administrative expenses"]["2019"]
selling_2018 = df["Selling, general, and administrative expenses"]["2018"]
answer = (selling_2019 - selling_2018) / selling_2018 * 100.0