4/5 + ( - 2,8) × (2 1/3 ÷ 2,8 - 1)

4/5 + (-2,8) * (2(1/3) / 2,8 - 1). Выполним деление в скобках. 2(1/3) / 2,8 = (7/3) / (14/5) = (7/3) * (5/14) = 5/6. 5/6 – 1 = 5/6 – 6/6 = -1/6. -2,8 * (-1/6) = (-14/5) * (-1/6) = 14/30 = 7/15. 4/5 + 7/15 = 12/15 + 7/15 = 19/15 = 1(4/15). Ответ: 1(4/15).