1) -1 3/5 - 1/4 = -(1 3/5 + 1/4) = -(1 12/20 + 5/20) = -1 17/20

2) -1 1/9 * (-1 17/20) = 1 1/9 * 1 17/20 = 10/9 * 37/20 = 37/18 = 2 1/18

3) 2 1/18 + 2,5 = 2 1/18 + 2 1/2 = 2 1/18 + 2 9/18 = 4 10/18 = 4 5/9

Ответ: 4 5/9