3) 19 * 2 55/76 - 39,4;

19 * (2 + 55/76) - 39.4 = 19 * (2 * 76 + 55)/76 - 39.4 = 19 * (152 + 55)/76 - 39.4 = 19 * 207/76 - 39.4 = 207/4 - 39.4 = 51.75 - 39.4 = 12.35
Ответ: 12.35